Raspberry PI Zero should work as Router and Fileserver (FTP)
Also planning to connect via Telnet/SSH
Longtime-Plans include maybe a bbs-server including Dial-In-Modem if i can find a cheap one
I bought a USB to DB9-Adapter and a db25 to db9 Cable via Amazon for connecting Amiga via RS232 to foreign hosts.
There is a nice Manual wich seems suitable and Promising: