Also played on Linux. The resolution pop up was there on first load, and I played full screen.
Just a heads up: I cannot download your game through the Itch.io app, because it isn't clearly defined which platform it is for.
I made a short video about your game! It was absolutely enjoyable, and I look forward to checking out "Signalis" when it's ready!
I had this same problem! Unless it's supposed to be some sort of symbolic ending or something? Or maybe I'm just thinking too much.