So it’s hard on some phones. Lineage OS support also isn’t any indication of how hard it is to unlock. The more popular devices are all easy to unlock.

That’s just confirming it’s generally extremely simple.

Which would help how? If they are really going to make it much more difficult for custom roms it doesn’t matter what phone you choose.

Security is definitely a concern, so replacing it is recommended. I’m not sure about other browsers compatible with Chrome extensions though.