Bill,
There is no known to me TELNET for Z80, those BBS ran either DOS or a flavor
of unix like software [Netware, Venix, Minix] on 8088 or later than 1986ish?
maybe 286 or 386 hardware.
Telnet to a Rpi? to a serial line to the CP/M engine (or CP/M emulator on Rpi)
would be doable.
I have a copy f Dave Dunfileds Myhorizon that runs under dosemu on my linux machine
that is accessible via telnet.? So its very "doable".
Allison
