It works for me.

I did originally have some issues and did some searching that there used to be firefox issues that are now resolved. Mine were fixed by restarting my VPN, but otherwise no problems.

I use a separate FF profile. It has no addons, apart from Vencord and a custom userChrome.css to hide the top tab bar (as full screening it would obstruct swaybar). I then just made an xdg .desktop entry which opens canary.discord.com with firefox using that profile.
Overall it somehow uses less RAM (albeit with another FF instance open, so maybe some resources are shared) than the official App and all other forks (eg. custom electron version) I looked at. Nearly everything works, but:

• File upload for the soundboards is greyed out, switching user agents to chrome results in some obscure error
• Game activity does not work as the browser version cannot access the process list (Though that never even worked acceptable on Linux anyway)
• I did not manage to get xdg-desktop-portal to run properly for screen sharing on Wayland with Nvidia, as - bummer - the latter misses something in their driver. So no screen sharing for discord either
• You sometimes suddenly ‘rejoin’ a call/VC, which produces a very annoying sound every time. It’s either a problem with my connection or the browser version of discord (or both). Disabling join/leave sounds ‘fixes’ that

Overall all of those problems are a better alternative to the constant flickering that happened with all electron apps on my system if they are not interacted with for a few minutes (eg. by being on another monitor/workspace). That’s just distracting as hell and often even breaks functionality. And of course, Nvidia is at fault again. Like for 90% of other problems with my system.
::: spoiler Little rant: Some issues that happen on my Nvidia system (wayland) that are not present on my Dell Laptop w/ Intel HD graphics. I spent hours and days researching those Problems with potential solutions, very few improved some things a bit.

• Electron apps flicker
• Generally, windows with less than 60 FPS will flicker, with transparent stripes letting you see the background/wallpaper
• Firefox sometimes just freezes whole websites, you need to un- and reload the site to continue using it. May be related to hardware accelerated mode tho.
• One update temporarily let games in full screen freeze. Even after killing them. And it still displayed after switching to a tty and back. And it even persisted killing the wayland session. It was just a frozen picture on output 2 forever, while in graphics mode.
• Features such as sharing the screen via xdg-desktop-portal do not work :::