That's pretty awesome.
How are you doing it?
Successful manual coinjoin with three Trezors via Electrum Wallet 💪
https://mempool.space/testnet/tx/5443cf72fedb85b911ac0164686771dffb43266c5e87d7f8ddf19deaa9b70045
Discussion
More like joint transaction?
Pretty manually.. Here are the steps for two parties 🙂
https://github.com/spesmilo/electrum/issues/8910#issuecomment-1961280680