Faxes, like modems, require an absolute timesync between the ends of the link. Packet networks are not designed to provide this, and a horrible hack (ITU T.38)

Faxes, like modems, require an absolute timesync between the ends of the link. Packet networks are not designed to provide this, and a horrible hack (ITU T.38) is implemented in VoIP systems to fake it.Having had to debug an implementation of T.38 once, I expect that after a while no-one will bother to maintain it and these devices will stop working.Or they will just work only over email or some other mailbox system.