This is incredibly simple on linux.  This is the only way I have ever created Pi cards, other than actually creating the partitions myself and copying filesystem content over (usually for backup-restores, duplications, pre-sizing, etc).  I may have done it a hundreds times and have absolute confidence in it.  I believe the same methodology works on Mac although I am not a Mac user so won't promise.

The images come zipped/compressed, extracted from which you get, eg., `2024-07-04-raspios-bookworm-arm64.img`.  You need to know the device node of the SD card; I normally use a USB adapter so it shows up as, eg., `/dev/sdc`.  If the card is already formatted, there will be a `/dev/sdc1` as well -- that is **not** what we are interested in, we need the card, not a partition on it.

Partition on the card **should not be mounted** when you do this.  If your DE or something automounts, make sure it is "ejected"/unmounted first.  *What is currently on the card is irrelevent*.  You do not need to erase or format anything, doing so will be meaningless.

    dd if=2024-07-04-raspios-bookworm-arm64.img of=/dev/sdc bs=4M

That's it.  I'm not sure that the block size really matters (it may affect the speed of the write), that's the one I've always used.  For information about `dd`, see `man dd`.

You can do a crude verification with `fdisk -l` by running it on the `.img` file and then on the device node.  The partition names (the "Device" column) will be different but everything else should match up (for current Rpi OS images, two partions, the first small (< 1GB) one `W95 FAT32 (LBA)` and the second larger one `Linux`.

> I understand that Imager might be doing something more sophisticated that I don't.

Potentially, but not necessarily, yes.  I have never used it, but from my work here am aware it can do things like pre-configure networking, etc.  The image as is, copied above, will boot to a `raspi-config` interface the first time (I don't think the imager changes that, although I think it is developing in that direction, ie., to potentially replace that functionality).  You can mount the card before you use it and modify things yourself, of course.