A solution to this is Nostr. One identity across the entire network.
Twitter-like Platform/client dies overnight? No problem, all data still there.
Reddit-like platform/client dies overnight? No problem, all data still there.
PC dies overnight? No problem, all data still there.
Data is sync’d across multiple relays, you can run your own, and clients are interoperable.
It’s my go-to now, for everything. A person’s posts, their followers/audience, chats, etc never needs to be migrated.
Media is stored using the Blossom protocol which was created for Nostr.
V4V(Value 4 Value) is also a thing, so instead of just Likes/Reactions you can tip/Zap Sats (Bitcoin over Lightning) but that’s optional.
It’s not centralised though. It’s quite decentralised actually.
As for your “nazi bar problem”, I’d suggest you review the relays you connect to. That’s the beauty of free speech, and power of choice.