Yes, I'm also interested in ARM because it means we can have a very light laptop / tablet running a full desktop OS without the typical limitations of iOS / Android.

Debian is for sure the most stable thing in ARM, mostly because it is the upstream of many ARM-focused distributions like Armbian and there's also where ARM CPU makers usually test their stuff. There's a constant stream of patches coming from those manufacturers and downstream distributions because everyone wants to mainline both kernel and userland support for their ARMs.

Unfortunately there isn't much decent "open" tablet hardware to run Linux on. The interesting things like those ultra-thin Lenovo tablets with amazing screens have locked bootloaders and other bullshit that stops people from loading Linux into then and making drivers / the required adjustments. Then there's the Pine stuff that (even if you can get it) it's overpriced, bulky and not a finished hardware product in any way.