Raspberry Pi fails to boot when volume label is "boot" (e.g. after overwriting Raspbian)
Raspberry Pi fails to boot and repeatedly blinks LED 7 times, meaning "kernel not found". If BOOT_UART=1 is set, the messages "Failed to load 'boot/initramfs-rpi' - initramfs disabled" and "No compatible kernel found" are printed to serial. This is caused by the volume label being "boot", which Raspbian/Raspberry Pi OS have in their official images: https://github.com/RPi-Distro/pi-gen/blob/225f69828fa05361d6028edf2d7a69db73fe2b45/export-image/prerun.sh#L77.
Many, many users have fallen for this: #10302 (closed), #10443 (closed), #10930 (closed), #12031 (closed), #12066 (closed), and #12361 (closed) at least, plus most likely #9979 (closed), #10407 (closed), and #11779 (closed).
The direct fix is to set the volume label to anything other than "boot". mkfs.fat sets the volume label to "NO NAME" by default, and I don't think any major operating systems use "boot". To change an existing filesystem from Linux, fatlabel will do the job: fatlabel /dev/sdX ALPINE for example. However, I think we should rename the boot directory in order to mitigate this footgun. In the long term, I agree that we should move to image-based distribution anyways.