Self promotion but relevant:
I have a hobby business doing something very similar, except I focus on a specific model—pretty much the most power efficient PowerPC desktop Mac you can get that can still run Mac OS 9, the Mac mini G4. It's at https://os9.shop
Excellent!
This made me remember that I've still got a G4 Mac Mini! I was bringing up a current Linux on it, last time I had it running. 2019, perhaps.
I need to fire it up...