I am using Lineage but not really sure if it qualifies, it is still an android. Overall, it is pretty good. The main issues I am getting is due to the fact that I didn't install version with Google services, and I am using MicroG instead (open source implementation). Some applications don't like it, and you have to do some trickery with rooting to have a chance to run them (for example our national identification application), but it is pretty rare.

I would recommend it if you want to still be able to use everything you need but want a bit more FOSS experience.