It will really depend on use case. The most straight forward one is using LineageOS and F-Droid. With more specifics, I can give you a better fitting setup.
S20 FE? My understanding is that there arenโt many custom ROMs for this phone.
Yeah IDK if you are even able to get the bootloader onlocked for your version. Regardless, there is still a lot that you can do with stock. You can disable most of the Google stuff through ADB and install F-Droid. Neo store even has backgroud updates for Andrpid 12+ IIRC. Here is a short guide: https://www.reddit.com/r/degoogle/comments/jqxe1u/tutorial_how_to_degoogle_any_android_phone/
I canโt vouch for performance or update breakages though.