Mic support doesn't work yet, but you can listen to calls and use text chat.
Chat platform Discord is sort of usable on the Xbox Series X due to a new version of the console's browser.
As shown by The Verge senior editor Tom Warren on Twitter, the current test version of the new Edge browser is capable of running web apps, thanks to the fact it is built on the open-source Chromium tech, inspired by Google's Chrome service. This is currently available to folks signed up to Microsoft's Alpha Skip-Ahead program.
The browser is still in alpha testing. As it stands, you can load up the web version of Discord to use text chat, and even join calls - but mic input doesn't appear to work just yet. It's not clear whether this is something that will be fixed for the full release.
News that a new version of Microsoft's Edge browser was coming to Xbox consoles broke earlier in March, introducing a lot of interesting features. The software now allowed support for features including extensions, vertical tabs and Collections. You can also seemingly use Google's Stadia via the same browser, in addition to other streaming platforms like Nvidia's own Geforce Now, which allows users to play games from PC platforms like Steam and the Epic Games Store.
There are also reports, of course, that Microsoft is one of many suitors that Discord is currently discussing a potential sale with. The chat app is said to be valued at over $10 billion – almost three times what it was reportedly worth in June 2020. Discord might also simply go public, some sources have said.