I have no idea, either, but the Trezor team has confirmed on their Twitter that they are working on a CoinJoin implementation: https://nitter.net/Trezor/status/1566708740597972997, and Wasabi Wallet team is excited about "hardware wallet coinjoins."
Credit where it is due, what they have come up with is impressive, but unfortunately it is rendered completely useless by their surveillance and censorship.