Unfortunately they only support M1/M2 (last time I checked - hardstuck). It would be a great choice to repurpose existing hardware, but I wouldn't go shopping for Asahi specifically.

It sounds like they already are, and questioning what benefits having a remote MacOS server would give them.

Time Machine backups could be one reason?

Time Machine does not require Mac. You can point it to e.g. a SMB share as destination as well.