It’s worth noting that the issue you describe is to be directed mostly to developers uploading their Linux builds on Itch.io, not the site or its creators themselves.
Each developer is responsible for uploading builds that any use can run with as little hassle as possible. Devs also have the option to provide instruction, for more complex projects if they want to.
I can agree that support for tar files would be a nice extra for the Itch.io app (I haven’t checked if it’s already there, so I’ll take your word for it that it isn’t). However using zip files is not really impacting the project in any way.
The experience goes like this; The user finds a software that they wish to try, they click download, select the appropriate file ( usually labelled linux_64bit ), after it has finished downloading they click launch and - nothing happens. No error message, no console output. The only console output you get is “App launched, getting out of the way”.
That’s a fair point, I’m not sure if the Itch.io app can detect a game that failed to run. However similar to above, if a game fails to run, but exits without an error, there is no way for the Itch.io app to know if that’s intended or not.
Hope that makes sense, there was a lot that you posted, so not sure if I missed anything. Most of the things I’ve mentioned are based on personal experience - most of my projects support Linux. :)