This ran perfectly for me as well using the latest Proton beta. I played the whole thing through twice to get 100% of the achievements. There were no issues; it had solid performance the whole time. I didn't have to mess with any flags or anything.
system specs
Nothing extracted yet.
Works great on Ubuntu Linux 18.04 LTS (nvidia gpu, steam controller)
Its short game, so I have finished it completely on Ubuntu. No problem.
My System Info