FireWire to USB-C
Wanted to add to older post but can’t. Cant get a web cam now due to demand, so dug around found old iSight cam from 2004 or so.
Connected its 400 fw plug to a 3rd party adapter to get 800 fw interface, plugged that into Apple 800 fw to Thunderbolt, plugged that into Apple Thunderbolt to USB-C, plugged that into my MacMini, and guess what - it works!
Mac mini 2018 or later