It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Gede: I noticed that Not a Hero has Linux support, while the Global MegaLord Edition has not.

Is this some sort of oversight from GOG or is there some other justification to it?

Thank you for bringing our attention to the issue. I'll see what can be done here.