BUG: Multiple Keyboards Lag

[Ryan McClue]

PROBLEM:
I'm on a fresh install of Ubuntu 20.04 (xorg 1.20.11), with 2 connected keyboards (built-in and USB).
When I hit keys on each keyboard simultaneously in a program like firefox, gnome-terminal etc. stalling/lag occurs.
It only happens for keyboards it seems as moving an external mouse and trackpad together causes no issues.

TO REPRODUCE:
To investigate the problem I wrote a simple C file (see attached 'xorg-lag.c', compile with $(gcc xorg-lag.c -o xorg-lag))
The program finds keyboard devices under /dev/input/event and uses epoll to poll them for input via the evdev interface.

If I start entering keys on one keyboard and then switch to the other, the program stalls briefly.
If I simultaneously enter keys on each keyboard the program stalls indefinitely until I stop entering keys.
I have tested with different keyboards and experience the same result.
If I switch to a virtual terminal and run I experience no lag.
This makes me think it is a bug with xorg.

--
Ryan McClue, Sydney
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