An actually relevant link: this BIP natively allows encrypted P2P data transfer on the Bitcoin blockchain.

I don't see any silent spending feature in Bitcoin Core itself, but I see a lot of positive building blocks.

Taproot could possibly be used to add signature rings to Bitcoin transactions since it is very scriptable, but this would be complex and require special support in wallets.

If there's something I missed here, I'd be happy to see it.

https://github.com/bitcoin/bips/blob/master/bip-0324.mediawiki