For airgapped signing devices like SeedSigner, Sparrow is the best I've come across. Not totally sure, but Specter is also used for airgapped multi-sig purposes. For mobile, I think BlueWallet can be used for airgapped signing, but I wouldn't recommend using a mobile device for that use, as they're designed to connect to as many networks as possible (which is the opposite of airgapped).

I don't think there's multi-sig taproot support in any of these wallet software yet.