I guess thats the only other thing - it could be my null modem cable.
Have attached some piccies.
Typing stuff in TERM mode on Tandy 102
Echoed out using picocom on ubuntu
So I know it "can" work.
For the TI, have now tried 3 different serial->usb convertors (left of piccie)
The middle one has FTDI. The top one is the one I use with the Tandy.
This is the null modem cable I am using
Settings in Mass Xfer
Typing stuff in Terminal mode
Nothing appearing in Ubuntu. Tested with all 3 serial->usb converters.
Will keep on playing, will try another null modem cable. Or maybe a proper serial device on an old PC.