Further on-chain communications:

https://mempool.space/tx/91271efcbb5ab29abfc38ae635f0644e3ba... "Please contact [email protected]"

https://mempool.space/tx/bd81219691eb1e22475c5985d847fa888c3... from Blockstream, unknown PGP message

https://mempool.space/tx/3a3eac4a26395b8c2563aaf1eb8b1b77798... from attackers, "sending most back to bc1qdlld6antmv4xug242ed83q7k4rqw50cwfns38szx4qu2f4jwaxxsuhwxxr, is that ok"

https://mempool.space/tx/8a444eed65c4584f138e08ee138f61490ef... from Blockstream, PGP-signed "Yes, thank you."

https://mempool.space/tx/83825b2135dd0abac12c9dfe17f29ab81b3... from attackers, "Please fix the bug first. The chain is under risk at latest commit right now. Make sure every node is patched. Then we will transfer the money back safely after confirming the fix. The detail is as follows (encrypted using https://blockstream.com/pgp.txt)." with unknown PGP-encrypted payload

As of writing, no response from Blockstream, and funds are still controlled by the attackers.