I don't have an answer (yet), but I am tracking on KaiOS[1] for a future replacement. Once there is some decent and accessible hardware behind it, I feel it may be my next 'upgrade'. There's the Nokia 8110[2] but it's not available to me yet.
But note that KaiOS itself doesn't ship devices, so we can't publish some of the code used by OEMs to do full builds.
While I agree that we took too long to publish this code, we were not legally infringing any license contrary to what some (even at Mozilla, lol) pretend.