The days were simpler back then, heh.
Currently Godot 4 doesn't export to HTML with C# code (my case). The game initially was made with Godot 3.5 and exported then with no much problem. Using the GLES2 backend. For the devlog series I upgraded the project to Godot 4.
I heard shader compilation could be an issue?
Hm, found that issue - https://github.com/godotengine/godot/issues/70691 It's being worked on.