I have three browsers installed, each set to a different level of default security (medium, high, and "why would you ever click that link" super high). Firefox is my default browser (set to "high") unless I need the abilities of the others. I have Thunderbird set to "Ask" if I click on a HTTP or HTTPS link in a message. This way, I can select the amount of security I want when opening a link. Interestingly, though, Thunderbird presents the three installed browsers (Firefox, Vivaldi, and Google Chrome) - but it lists Firefox 3 times (see attached image). It shows "Firefox Web Browser" twice at the top of the list, and just "Firefox" at the bottom. BTW: Firefox is installed via apt-get and NOT snap or flatpak. Thunderbird is also installed via apt-get. Does anyone know from where/how this list is populated? I cannot find it anywhere in the UI or about:config.