Playlists, history, subscriptions and settings are all stored as .db-files in ~/.config/FreeTube (or whatever path it is if you are using the Flatpak). Sync those :) On FreeTube Android, you have to turn on custom data storage path in the settings first.
I’m on Fairphone 4 with CalyxOS, and I am happy with that. I would not expect them to release a Fairphone 6 anytime soon, so unless OP has all the time in the world, the Fairphone 5 should be good if they want to go this route.