Unfortunately, the fix I posted above did not work long term for me. I have an M2 Pro Mini that I share an external hard drive of to serve as a Time Machine destination for a M1 MBA and an old Intel MBP.
when I reboot the computer, I lose file sharing. to get it back, I have to do this process at least once (and as many as four times):
1. remove external drive from file sharing
2. Turn off file sharing
3. Reboot
4. Turn on file sharing
5. Add drive back to file sharing
it typically takes do the above five steps two times before file sharing works again.