Rich (product manager(?) for Jade) said that they're working on QR signer support in Green "soon" which would open the door to at least Specter DIY and potentially SeedSigner if we were to implement Liquid support.

I would need to see at least one more production-quality wallet add Liquid support w/airgapped signing before feeling confident in investing time to build on Liquid.

With Specter Desktop off the board, I'm not aware of any second wallet option out there.