There are lot of ways nowadays to move files between vintage Macintosh and modern OSes like the actual, unix based macOS 12, Monterey. You can use lot of different solution to use SD cards like harddisks (SD2SCSI, MacSD, blueSCSI, RaSCSI, etc) or use the SD card like a floppy (e.g.: Floppy Emu) but for these solutions you have to invest sometime more sometime less money.
If you just want to kick-start your ever-first-just-arrived vintage Mac, and you have a cheap USB Floppy, then here is a solution for you. To create your first Mac floppy disk.
This solution works with any Mac from the SE up to the latest model with floppy drives, before the iMac G3. (Sadly it won't help you to read/write 400/800KB MFS disks for the very early Macintoshes. Topic discussed here bellow, in this thread)
Of course you can use some emulator (Sheepshaver or Basilisk II) to create a full size diskimage, and copy this disk image to the USB-connected floppy disk. This command in Unix-like system could look like this:

dd if=yourdisk.img of=/dev/yourmounted_floppy

You can modify on your vintage Mac, then copy back into your favorite emulator, do some changes there, copy into the diskimage and then the diskimage again to the floppy.
But there is a solution to access to the HFS formated floppy disk directly from your modern computer:
This is the hfsutils package from Robert Leslie.
The original website is here:
https://www.mars.org/home/rob/proj/hfs/
The downloadables are available on FTP as well:
ftp://ftp.mars.org/pub/hfs/

...and here is one of the many HTML based documentation.
https://linux.die.net/man/1/hfsutils

HFSUtils is old. The latest version is 3.2.6, it is from 02-Nov-1998!
The easiest way is to install over HomeBrew:

brew install hfsutils

It will create the hfsutils folder into the /opt/homebrew/Cellar but installing with brew not need to configure more.
In the Terminal you can use immediately.

Connect your USB floppy disk drive to your computer.
Put any 1.44MB disk into and wait till the macOS 12, Monterey (or your modern Macintosh OS) reports the disk is not readable on your computer. The window will ask you to "Eject", "Cancel" or "Format" the disk.
Don't do anything irreversible, click to cancel. The disk is in the floppy disk drive and connected over USB to you computer.
If the disk was formated to FAT12 or exFAT then the modern Mac will be able to mount it, then "drop to the trash", but don't remove from the drive!

Open the Terminal and type:

diskutil list [Enter]

You should see something similar:

/dev/disk0 (internal): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme 1.0 TB disk0 1: Apple_APFS_ISC ⁨⁩ 524.3 MB disk0s1 2: Apple_APFS ⁨Container disk3⁩ 994.7 GB disk0s2 3: Apple_APFS_Recovery ⁨⁩ 5.4 GB disk0s3 /dev/disk3 (synthesized): #: TYPE NAME SIZE IDENTIFIER 0: APFS Container Scheme - +994.7 GB disk3 Physical Store disk0s2 1: APFS Volume ⁨Macintosh HD⁩ 15.7 GB disk3s1 2: APFS Snapshot ⁨com.apple.os.update-...⁩ 15.7 GB disk3s1s1 3: APFS Volume ⁨Preboot⁩ 773.4 MB disk3s2 4: APFS Volume ⁨Recovery⁩ 835.9 MB disk3s3 5: APFS Volume ⁨Data⁩ 690.7 GB disk3s5 6: APFS Volume ⁨VM⁩ 20.5 KB disk3s6 /dev/disk4 (external, physical): #: TYPE NAME SIZE IDENTIFIER 0: *1.5 MB disk4

Search the disk with the (external, physical) 1.5 MB size. Remember for its Unix path: /dev/disk4 - in this example.
First need to mount the disk content into the Unix(macOS) environment with the hfsutils - hmount command:

sudo hmount /dev/disk4 [Enter]

It will ask a sudoer's password (probably your user's password), and then you should see similar content:

Volume name is "Transfer" Volume was created on Mon Nov 7 20:33:04 1921 Volume was last modified on Mon Nov 8 12:49:13 2021 Volume has 1402368 bytes free

Remember for the volume name, now is "Transfer" yet.
If you want to format the disk, or previously was not HFS formated, use the following command:

!!! IT WILL ERASE ALL DATA !!!

sudo hformat -f -l "New disk" /dev/disk4

Volume name is "New disk" Volume was created on Tue Nov 9 18:25:12 2021 Volume was last modified on Tue Nov 9 18:25:12 2021 Volume has 1448960 bytes free

To copy files to the newly formated disk, use the hcopy command:

sudo hcopy "./stuffit55.hqx" "New disk:stuffit55.hqx"

Recognise the colon, as separator between the volume name and the file name.

There is no progress indicator, when the copy procedure finished, you'll get back your prompt. You can check the contet of your floppy:

sudo hls -la

The result:

f APPL/STi0 319095 505470 Nov 9 18:36 stuffit55.hqx

Copy one more file to the disk:

sudo hcopy "./Thread_Manager_2.0.1.sea.hqx" "New disk:Thread_Manager_2.0.1.sea.hqx"

List again the content:

sudo hls -la fi FNDR/ERIK 2864 0 Nov 9 18:43 Desktop f APPL/STi0 319095 505470 Nov 9 18:36 stuffit55.hqx f INIT/thds 14438 13248 Nov 9 19:03 Thread_Manager_2.0.1.sea.hqx

But we're not ready yet, INIT/thds is not that want we want, have to set the Type and Creator code, otherwise the old Macintosh System will not recognise the Thread Manager as a HQX.
Use the hattrib command to set the correct Type and Creator codes:

sudo hattrib -t TEXT -c BNHQ "New disk:Thread_Manager_2.0.1.sea.hqx"

sudo hls -la fi FNDR/ERIK 2864 0 Nov 9 18:43 Desktop f APPL/STi0 319095 505470 Nov 9 18:36 stuffit55.hqx f TEXT/BNHQ 14438 13248 Nov 9 19:03 Thread_Manager_2.0.1.sea.hqx

To check which file has what Type/Creator code, check this website of Pierre Duhem:
https://www.macdisk.com/macsigen.php

With this easy, few Terminal command you can create the very first disk for your Macs and possible to use HFS formated disk to transfer files directly from the modern Mac to the vintage Macintosh.

This is some excellent content, and i'm stickying this to make sure it remains visible!

How "Modern"? I believe up until support was dropped in Mac OS X 10.6 it could still mount HFS disks / images.
There was an HFS FUSE filesystem project that could reenabled that in later OS versions but I believe it stopped being worked on some time ago.

>> OXTPaul said:

How "Modern"? I believe up until support was dropped in Mac OS X 10.6 it could still mount HFS disks / images. There was an HFS FUSE filesystem project that could reenabled that in later OS versions but I believe it stopped being worked on some time ago. Click to expand...

Modern mean: Big Sur, Montery - latest Intel based Macs and the latest M1 Macs.
Of course if you have a G4 iMac or PowerMac G4 then the same USB floppy disk drive will work as fine for HFS disks under Mac OS 9.2.2.

Looks like no one has updated FuseHFS filesystem for OSXFUSE since 2014, but OSXFUSE says it supports macOS 12:

A very useful alternative while using a modern Windows machine (applicable from Windows XP to at least Win10 and in all probability, Win11 as well) is:

HFVExplorer - a standalone virtual HFS disk image creator/editor. It also loads and interacts with 1.44 mb real physical disks just fine through a USB floppy drive, which is my own favorite no-fuss method to bring small enough files to my Classic, SE/30 or PB180.

it can be used to aid you in the chicken and the egg problem when you set up your very first emulator. You can use it to poke disk images and add & delete files without needing a working vintage OS environment at all.

Thanks for writing this up! i'm def gonna try it out.

Would it be easier to say that this only works with 1.44MB disks? A lot of my Mac SE's are the non-superdrive version. (they only do 400k/800k)
and as such. i don't think this will work.

>> Patrick said:

Thanks for writing this up! i'm def gonna try it out. Would it be easier to say that this only works with 1.44MB disks? A lot of my Mac SE's are the non-superdrive version. (they only do 400k/800k) and as such. i don't think this will work. Click to expand...

No, sadly, not. It will work only with SuperDrives (and with the 1.44MB USB floppy drives). It is in the original text, maybe I will highlight it.
The 400KB or 800KB drives are completly different - they're changing the rotation speed based on the sector where the read/write head is. In this was they can keep the sector phisical size equal on the whole surface of the disk. (Inner region has less sectors, outer regions have more sectors (because of the longer diameter of the disk)).
The SuperDrives and PC floppy drives are fix rotation speed disk drives. That disk what is 400KB (or 800KB) in a Mac that is 360KB (or 720KB) in a PC drive. It has greater sector's lenght at the outside regions and shorter sectors inside.
BUT: DO NOT FORMAT a disk in a PC drive if you want to use in a Macintosh floppy drive. It is more important for the very early 400KB disk drives arrived in the original Macintoshes.

Very good sources about the topics:
400k and/or 800k Floppies with an External USB Floppy Drive

Apple and the Floppy Drive

Hi @fehervaria! :) [wave]

AWESOME guide! [grinning-face-with-s] Thank you. [person-with-folded-h]

I want to clarify. After a 1.44 MB 3.5" disk is formatted in HFS following your guide in OS X on a USB 1.44 drive, can the disk be read and written to on a Mac with a 400k or 800k disk drive? That those Macs only can see up to 400k or 800k?

>> retr01 said:

Hi @fehervaria ! AWESOME guide! Thank you. I want to clarify. After a 1.44 MB 3.5" disk is formatted in HFS following your guide in OS X on a USB 1.44 drive, can the disk be read and written to on a Mac with a 400k or 800k disk drive? That those Macs only can see up to 400k or 800k? Click to expand...

No. Those first generation Macintosh models with 400k or 800k drives are entirely different. Not only the size than the way of data management is different. The ROM and the IWM contents too.
Only the Apple SuperDrive able to handle "modern" floppy formats (PC and Mac) because the data storage way is similar: fix rotation speed.
The "old" Apple drives are changing their rotation based on the sector (the head position over the disk surface).
Please read my previous post: Post 8

If your question was about the disk formatted with 1.44 drive possible to use in an 400k or 800k drive, than the answer is "no" again, because you have to cheat and cover the HD slot on the 1.44 floppy disk. Then need to reformat in the 800k drive... but it is absolutely not recommended.
High Density disks and Double Density disks are - again - very different.
If you have a Macintosh 128/512 with 400k disk drive, please use only 400k low density disks (400k in Apple's names and 360k for the PCs). Don't format them in other drives (like PC floppy drive or modern Mac's floppy drives)!
The magnetic field generation power is very different for high density disks and for their drives than for the low density disks and those drives.

>> fehervaria said:

If your question was about the disk formatted with 1.44 drive possible to use in an 400k or 800k drive, than the answer is "no" again, because you have to cheat and cover the HD slot on the 1.44 floppy disk. Then need to reformat in the 800k drive... but it is absolutely not recommended. High Density disks and Double Density disks are - again - very different. Click to expand...

Ah. Thank you for clarifying. :)(y)

>> fehervaria said:

If you have a Macintosh 128/512 with 400k disk drive, please use only 400k low density disks (400k in Apple's names and 360k for the PCs). Don't format them in other drives (like PC floppy drive or modern Mac's floppy drives)! Click to expand...

Right.

>> fehervaria said:

The magnetic field generation power is very different for high density disks and for their drives than for the low density disks and those drives. Click to expand...

Nice to know. Thank you. :)[person-with-folded-h]