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But if something needs dedicated servers, then I'd argue if it's really decentralized?

dPoS while a decent solution is already setting up some centralization. We shouldn't add more centralization to the Steem ecosystem.

Absolutely agree. We shouldn't add more centralisation.

However, now that WebRTC is widely supported by browsers I believe videochat can be done without the need for centralised high-bandwidth servers.
For decentralised file-storage there are also some interesting projects live already. IPFS (which i think is used by d.tube) or blockchain based like Sia or Burst.

If you ask me, chat messages shouldn't necessarily be stored. It can be session-only or DOM-only. It has its drawbacks UX-wise but I'd consider it safer than permanent chat recording like in Facebook.