It's not 32 bit computers, but computers with a 32 bit BIOS clock. There is fortunately a difference.
GitLab is working on federation last I checked.
I know you said you've ruled out Onyx, but I just purchased the Boox Palma, and I really can't complain about the quality of the device. It's light years ahead of anything by Kobo, which I was considering.
I didn't realize that Onyx is a GPL violator until after I purchased the device, but they really engineered an awesome little solution otherwise. Conflicts of interest are hard. :-(
In this case, a good pubic education.
I'm not disappointed - I'm tired of getting harassed by their doormen and the kind of people it attracted.
I also recommend Joplin - I've moved my entire journal over to Joplin and use it as a primary note source now.
The mobile app UX is its weakness, but is fully functional.