Technically there are third party clients, they just break tos and can get you banned if you're not careful. Ripcord has a lot of cool features, I just wish I could risk using it.
That's just it, they're so hostile they ban people for trying to use their service. Plus their API changes often enough to make it an annoying game cat and mouse for the devs. There are two discord clients for plan 9, both at one point worked, both are now abandoned. It's not at all worth it.
