This is neat. I’ve been thinking about doing something like this on my Quest 3, but it’s a fair bit bulkier than this setup. One upside is, you already get an Android and can setup pretty much anything you might want! (I’ve sideloaded F-Droid on mine, going to see if Termux works.)
Re: Bluetooth keyboard – you can get a Thinkpad keyboard as a Bluetooth one. It’s slimmer that the usual bottom half, so it’s much more portable. But it’s not folding, of course.