How to address error "Did not load script at 'script name' because non script MIME types are not allowed when 'X-Content-Type: nosniff' is given
I want to just delete the question but I hope maybe this answer will still be helpful to someone.
So, my problem was actually that I had a bad clone of my project and it was missing files!
However, for anyone having the same issue:
ensuring that type="text/css" for stylesheets and type="text/javascript" did fix the issue. (for the files that actually existed)
Please make sure that a response header with the name X-Content-Type or X-Content-Type-Optionas has the text/javascript value instead of nosniff.
It is simple to make a workaround locally using Charles Proxy Rewrite tool
