If you're one of those people who drank the wrong flavor of kool-aid, you end up running Discord on Linux and wondering why audio doesn't work. Audio doesn't work because Discord is running under Xwayland, probably, and the app you want to screenshare with audio is using Wayland, not Xwayland, and simultaneously, you're using Pipewire instead of Pulse directly.
As of December 25, 2025, the best solution I've found is to run the Flatpak version of Discord and screenshare by explicitly forcing whatever audio device is being captured to use pulse as the audio server. You can do this in some applications by setting the output to pulse directly. Some applications do not support this.
For example, if you want to use mpv and screenshare it, you can use mpv -ao=pulse file.mkv to screenshare file.mkv in Discord and have it capture automatically.
Incidentally, Firefox works out-of-the-box, which is interesting.
qpwgraph is a nice Qt GUI that will tell you what the heck is going on with your audio. If you can't share audio with Discord, you can drag the audio's outputs to a Discord game capture interface if one exists manually.