When UTF-8 wasn't univeral (geez, I'm old... It was still this century though!), a page I found to figure out what was going on when I encountered Mojibake is: http://www.jeppesn.dk/utf-8.html . Amazingly it hasn't suffered linkrot and is still online.

And I fully agree with footnote 2, why is an extended Unicode character being used in place of the apostrophe? https://tedclancy.wordpress.com/2015/06/03/which-unicode-cha...

Martine écrit thought she was an ugly duckling. In reality she was a UTF-8 swan.