Official Mozilla response:
https://discourse.mozilla.org/t/certificate-issue-causing-add-ons-to-be-disabled-or-fail-to-install/39047
"Certificate issue causing add-ons to be disabled or fail to install:
10:50 a.m. UTC / 01:50 a.m. PDT: We rolled-out a fix for release, beta
and nightly users on Desktop. The fix will be automatically applied in
the background within the next few hours, you don’t need to take active
steps.
In order to be able to provide this fix on short notice, we are using
the Studies system. You can check if you have studies enabled by going
to Firefox Preferences -> Privacy & Security -> Allow Firefox to install
and run studies.
You can disable studies again after your add-ons have been re-enabled.
We are working on a general fix that doesn’t need to rely on this and
will keep you updated.
See the latest updates here:
https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/
"
Firefox from the Debian package has data reporting disabled so using
studies is not possible.
