@sigsegv I enjoy Etar as a calendar app, other than that I can second @najodleglejszy on a lot of apps like Organic Maps (especially great for hiking) and the Kiss launcher. Firefox is my browser of choice.

If you want to go the whole mile, #UbuntuTouch works great on the Fairphone 4 (with Android app support under a compatibility layer), and #postmarketOS is maturing fast for the device. So leaving Android behind entirely is a real possibility!