I just installed Adventure Game Studio 3.5 on Focal Fossa. I had to install the .NET framework with Winetricks, and that worked, which is how I was able to install AGS.
When I try to open AGS after installing it, it comes up with this error:

Screenshot at 2020-05-20 13-20-22.png

I'm kind of a "fake fan" who doesn't know how this platform works, so keep that in mind.
Thanks in advance!