Did a live stream yesterday, where I tried to set up a serial tty connection between my Psion and an old RaspberryPi I had laying around. Got most of the way there in an hour, even though I had to spend some time troubleshooting what turned out to be me forgetting to plug the damn cable in. But then got stuck on it not accepting my login credentials, just reloading the login screen. I did some reading today, checking Man pages and documentation, and forum posts. turns out I was missing a "-h" flag/argument(not sure about the correct term) in my serial-getty@ttyUSB0.service configuration file. And that I could keep most of the settings there by default, but without "-h" rtc handshaking didn't work.
feeling pretty stoked!
Anyways I will try to do a complete write up once I'm done with my little project.
It is indeed an Ericsson branded Psion. Cool project. I wonder if those frequencies will become open once they discontinue them for regular cell transmission.