A similar build is arturo182's Handheld Feather Wing, which uses a Blackberry Q10 keyboard [2]
Though it doesn't have a processor of its own it can be plugged into Feather compatible boards that do (like @groguard's Giant Board, which runs Linux [3]). Makes quite a nice package!
I ended up going the other way and building a (split) 60% keyboard with a screen and a Pi in the middle [1]. It's long enough that you can sling it over your shoulder on a guitar strap, so it somewhat fails the pocketability test.
Another interesting build currently being polished up is SnapOnAir's Blaspberry v2. It's deemed a "communication tool". They've made a modern day pager as well, but the new one is like a linux blackberry that is entirely open source.
The developer has been in talks with arturo about working together on it (based on their tweets at least) using that q10 keyboard. It's pretty damn impressive and I've seen doom running on it (though that's not the highest benchmark).
I'm always a bit sad, that we don't see the compute module used in these kind of projects, especially when size does matter. But I understand it, they seem hard to source and expensive for hobbyists, which kind of defeats much of the open source spirit. Still, the form factor would work great for add-on boards.
https://www.reddit.com/r/cyberdeck - a reddit community for people who build similar things to your commute-deck, which I'm sure you're familiar with, but I thought I'd link for those who are not.
I ended up going the other way and building a (split) 60% keyboard with a screen and a Pi in the middle [1]. It's long enough that you can sling it over your shoulder on a guitar strap, so it somewhat fails the pocketability test.
[1] https://github.com/borgel/commute-deck [2] https://hackaday.io/project/165450-keyboard-featherwing [3] https://www.crowdsupply.com/groboards/giant-board