Interesting read. I wonder where OP got the specs for the device itself, i.E. what it expects in terms of data and what the response (interrupt) values mean?

They also offer Threema Libre on F-Droid for all us folks who degoogled their phone

They also created a standalone, story based Gwent card game that is pretty good, just in case you didn’t know: Thronebreaker: The Witcher Tales