I have been dealing with a bug with Ubuntu for the past year.
If I were to play any version of Minecraft 1.13 and up, It will have the problem of not allowing you to hit 2 or more keys at once, It will either do 1 of the keys or wait until they start repeating.
Its an issue that I want to fix, I don't know what to do or where to start.
Here is a video of the problem in action
Hopefully, this information is all you need to determine a proper fix.