I don’t think privacy enthusiasts use vanilla Android. People will stick to Lineage/Graphene for as long as it works and then switch to something like Postmarket. It’s already in a state where it’s rough but usable.

Signal is nice because it has a pretty good adoption rate even with non techies (which is why they’ve been mentioned by name in the chat control proposal). But privacy enthusiasts will still have briar/simplechat/xmpp. Those aren’t centralised like Signal and will be a lot harder to regulate