Hi, I know this post is 6 days old but I’d also like to add to it.
Since the latest update, Discord seems to have had a major performance impact and the source appears to be the Server sidebar. If you mouse up and down it vertically it immediately increases CPU resource usage somewhere between 20% and 30% and decreases FPS from 55 to 5. Running a performance profile on the client, between a range of 0 - 25 seconds, painting is taking up 18,000 milisecond of activity during this period, the problem appears to be how the client is painting the sidebar after every mouse event that interacts with listed servers. I don’t believe there is any available solution to this it might be something Discord has to fix.
I had a friend recommend I install this package which makes discord use your globally installed Electron, but I’m still having the same problem, perhaps you’d have better luck with it.