My first suggestion would be for you to test if the issue also occurs when you run KDE Plasma on Wayland.
Instructions for switching Plasma from X11 to Wayland
You can change your Plasma session from X11 to Wayland by selecting the session type at the login screen (Wayland is now KDE’s default for Plasma).
If you have set up autologin to skip the password screen, you can change to a Wayland session by opening System Settings → Colors & Themes → Login Screen (SDDM) → Behavior.
To see if your current session is running on X11 or Wayland, run the following command in a terminal:
echo $XDG_SESSION_TYPE
For those curious about how Wayland differs from X11:
My second suggestion would be for you to try launching discord from a terminal, and see if any errors or warnings appear in the terminal.
Finally, some system info would also be helpful. Please read the pre-prepared information below and post the output of inxi -zv8, correctly formatted according to forum requirements.
As a new or infrequent forum user, you are encouraged to take some time to familiarise yourself with Forum requirements; in particular, the many ways to use the forum to your benefit:
The Update Announcements contain a Known Issues and Solutions section and should generally be checked before posting a request for support.
Output of the inxi command (with appropriate parameters, and formatted according to forum guidelines) will generate information useful for those wishing to help:
inxi --filter --verbosity=8
or the short form (preferred):
inxi -zv8
- inxi man pages (Arch Manual)
Regards.