I am looking for a Firefox add-on that checks SSL serial numbers or fingerprints and reports changes to the user. I realise that SSL certificates can change at any time for many legitimate reasons, but that's okay. I am just looking for a notification that the security of a connection to a site has been changed.
There are quite a lot of add-ons for Firefox that do things with SSL certificates, but everything I've found so far is not compatible with Firefox Quantum. For example, Certificate Patrol looks like it would do what I want but it isn't compatible with modern Firefox.