This is an old one, but perhaps my comments will be valuable to someone.
I too recently started seeing this unsupported MIME type error followed by the ERR_INSECURE_RESPONSE error. It was regarding sw.js
sw.js seems to be a Service Worker implementation by NitroBay:
I was able to resolve the error by following the advice offered by n3tr:
I can’t say what caused the problem, though it is easily resolved. I am also not sure why my app is even referencing sw.js, it is currently a bare minimal meteor and react learning experiment. Does Meteor use sw.js now?