I already deinstalled all of my Unity-Versions, and reinstalled the recommended Version 2019.4.18f1 but everytime i try to build a project (even an unchanged one, with the SampleScene) to WebGL there is this error. If i build my project to Windows, everything gets right, but not for WebGL.
Yes. Give up on IL2CPP and set back-end to Mono.
The Mono scripting backend is not supported for WebGL, so this won’t work.
Can you provide the full details for this error message?
My apologies. This was my solution in Unity 2018. IL2CPP never seems to work for any platform. Very complicated to set up. I overlooked that OP is using 2019.
No problem, I just wanted to clarify. FWIW, the WebGL platform has never worked with the Mono scripting backend, even in 2018 and earlier.
How odd. Of me. To not notice that. Especially before posting. 
@Merlumbien I would recommend trying out with latest Unity alpha release as well (if you didn’t already).
We have historically had issues with paths that have uncommon unicode characters in their path names. But not sure if that would be the case here. If you can post the full logs like @JoshPeterson is asking, that would hopefully help out.
