That's definitely not the correct
SRI hash[
^] for the URL provided:
integrity="sha256-91EfQDvF2M3SQLvbAsWEh3Xg+J9t2VLnBnXSL9Q04bQ="
Assuming you've copied the error message correctly, then either the sites you're trying to access all used the wrong SRI hash value; the script file at that URL has been altered
(which should not happen); or there is something wrong with your internet connection or your browser.
Try running your browser in "safe mode", with all add-ins and extensions disabled. If the problem goes away, then you most likely have a malicious extension installed.
In any case, since it's not a problem with your own site, this question is off-topic. This forum is for questions about writing code, not for general IT support.