Ok, so I get to answer my own question. This is not an elementary OS issue, but rather a general Linux thing. Apparently, X likes to break inputs on upgrade.
To fix this, I just rebooted into recovery mode, enabled networking and dropped into root and ran apt-get install xserver-xorg-input-all
Just like that, I'm back in business.
I succeed solving this issue by luis_nando's answer. What I did step-by-step:
$ apt-add-repository ppa:netext/netext73 && apt-get update && apt-get install netext73
$ sudo netext73
Go through the first installation
Check Hibernate in the optimizer
found on Reddit Solution Fix