And it is, of course, closed source, so no way to use an alternative client. I wish I could use an IRC gateway for it, that would be cool (I very, very rarely use the voice chat)
Just because something is closed source, doesn't mean it's impossible to reverse engineer. The entire system is compiled into a javascript webpack, alongside just reading web requests/their documentation, doing some basic functionality in an alternative implementation is really easy.
This apparently breaks the terms of service, but they are only enforce this if you're an outlier for the number of API requests you send.
The most well known 3rd party client would be Ripcord, which I use for it's Slack features
This thing usually goes: Until the better client threatens the proprietary one with is better monetized.