Announcement of this project has been making the rounds lately and I think that it might be an excellent fit for an EOMA50 based phone/tablet (if and when those designs materialize).

https://ollieparanoid.github.io/post/postmarketOS/

Currently they are targeting only old phone hardware however, I think that their concept would work well for any phone/touchscreen device that is designed to have a long useful life. I may be wrong but, I think a OS distribution of this nature would be an excellent complement to computing hardware that is also designed to last much longer than the current norm.

-Mike