The psion series 5mx is a portable computer from the late 90s, here's my episode talking about it.

https://en.wikipedia.org/wiki/Psion_Series_5

PLPTools (syncing with modern linux): https://github.com/rrthomas/plptools

Nconvert (file converter): https://web.archive.org/web/20161130192611/http://neuon.com/downloads/nconvert/

Programming book: https://archive.org/details/book_20210531

psion linux SDK: https://github.com/static-void/psion_cpp_sdk_linux.git

Eric Lindsey's site, with lots of psion software: http://ericlindsay.com/epoc/index.htm

Apologies for talking quickly!