GrapheneOS

I'm using GrapheneOS on a second device for various reasons. The biggest issue for me is that not all apps work / run. However, I have limited app requirements, so that is fine. If you want to run all social networks, Uber, Lyft, and so on, there might be the one or other that doesn't work (I didn't try them all). However, you can always use the mobile web offering I guess.

In terms of classical smartphone features, I know what I don't get out of the box due to the lack of Google Services (Assistant, Picture Sync, etc). That wasn't an issue for me as it is a secondary device.