Yes it is browser playable! I exported it using Godot 3.1.2 and I think there may be several problems:
- The browser should support WebAssembly and WebGL2. Recent versions of Chrome/Firefox/Chromium should work.
- The downloaded and unzipped html5 version should be served through a web server. The simplest way will be invoking `python -m http.server` if you have python3 installed.
- About 12mb of files have to be downloaded before the game launches in browser.
I would like to add the Linux version but the uploading always failed. If you still cannot play the html5 version please let me know. I will tell once the Linux version is uploaded.