I don’t see how your issues with locking your bootloader affects the problem that you can’t use degoogled phones. that’s two totally different things.
fact 1: there ARE a lot of degoogled systems that support relocking the bootloader for a lot of devices.
fact 2: FP4 is in fact relockable, and /e/ as well as divestOS and iodéOS support it to be locked according to their installation guides.
I don’t know about your issues with netflix (i don’t use netflix) but it actually really seems to be related to an unlocked bootloader. Luckily, this can be fixed by locking it, at least with your FP4.
see this topic for example.
If you have issues with relocking, please ask for help in another topic. Good luck…