The numbering on the seasons is a bit weird. Going by the dvd numbering, it’s season 9, but by streaming numbering, it’s season 11
I’ve installed games from itch.io, and it’s about as easy as on windows.
Try setting firefox to your default browser. That made it work for me.
Except for that one section in Portal 2 /s
I think season 12 is better than season 11 so far, but not quite as good as the older episodes