This tutorial might apply to other HvH depots.
Install Lutris and wine-ge from the package manager of your choice.
Open Lutris, press the "+" button in the upper-left corner, select "Search the Lutris website for installers" and search for "Steam". Scroll until you find Steam (2003, Windows)...
so u use linux? want to play 2018 hvh? ur in good hands (i think)
first of all you want to get 2018 csgo downloaded and add it to steam as a non steam game:
after this find where you got your 2018 csgo and add 'csgo.exe' as a non steam game
NOW you want to run it at least once via proton...