Firefox 83.0 is rolling out, and this version has HTTPS-only mode, which, when you've enabled it, every connection it makes to the web is secure. It also alerts you when a secure connection is not available.
Here are the release notes for your viewing pleasure. [
mozilla.org...]
How to turn on HTTPS-Only Mode
Click on Firefox’s menu button and choose “Preferences”.
Select “Privacy & Security” and scroll down to the section “HTTPS-Only Mode”.
Choose “Enable HTTPS-Only Mode in all windows”.