You mean in the context of encryption decoupled from signing?
Discussion
Ideally, decryption should not be decoupled from signing. I know FROST doesn't support it. But we need to figure out something that does support. That will be better than decoupling.
Sounds like a tall mathematical order. Maybe (big Maybe) something like Paillier threshold encryption running alongside Frost. But Paillier won't work for an nsec so you'd need a Paillier key pair as an "aux" keypair. And this Paillier setup would be encrypting an AES key on top of that, since using Paillier itself for encryption of long messages won't work. So then you'd be juggling Frost shards and Paillier shards, and in the case of the Paillier shards they'd be shards of an AES key.
Basically the user would need to request from the client another keypair if they wanted to start using NIP44 DMs.
With a good UX it could be abstracted away like how this nstart thing abstracts away all the Frost complexity. Like the whole thing can be behind a single "Do it" button.
Disclaimer: that all could be very wrong. My team looked into Pallier for some contest gamification stuff a while back, it's good for voting on contest entries and stuff, but getting blurry in the memory.
Goodness me, all solved with Frost2x already. Those guys are trolling-ly good.