My Fairphone 2 died recently and I just today ordered a Fairphone 4 to replace it. I think I’ve used the Fairphone Open OS on the FP2 pretty much since the day I got it, but it seems like FPOOS is not being developed for the newer models? What is the “recommended” open replacement? Sailfish? Lineage? Something else?
I’d say LineageOS, but as far as I know it’s not really out yet, at least not in a reliable state.
iodéOS (which is based on LineageOS 18.1) is available for FP4 : iodéOS installation - iodé
and /e/ OS (also based on LineageOS) is also available for FP4: Info about Fairphone FP4 - FP4
iodéOS (based on LineageOS 19) and CalyxOS are available for testing. However, I would not yet use these for an FP4 as a daily driver…
Since you are coming from FPOpenOS, iodéOS might suit your needs best.
You may also have a look at the #oslist .