This bug has not been fixed yet.

Mouse cursor has disappeared. - Steam Community

https://steamcommunity.com/app/424200/discussions/0/2987537248818186130/

true. since that report is > 1 year old i guess the devteam wont fix it?

Dammit! Wish I'd have read this first, it really shouldn't be listed as playable on linux if it isn't.