Cannot run external script inside index.html

It is impossible to run any external script inside my index.html. I am getting the following message in the console:

Refused to load the script xxx because it violates the following Content Security Policy directive: “script-src ‘self’ ‘unsafe-eval'”. Note that ‘script-src-elem’ was not explicitly set, so ‘script-src’ is used as a fallback.

I tried to apply suggestions from Refused to load the script because it violates the following Content Security Policy directive
with no success. Any other idea?