I separately installed the Firefox Beta and Alpha channels, and have desktop configuration files pointing to them in
~/.local/share/applications. However, stable Firefox is being used as my default browser by the system. (Firefox Beta used to be used until I messed with the "Default Applications" in System Settings, where it is not listed.)
I tried running
sudo update-alternatives --config x-www-browser to manually change it, but it's only recognizing Chromium and Firefox (stable) and showing them as a choice.
What can I do to get custom desktop configuration files in
~/.local/share/applications to be seen as default alternatives? I think I may have to fiddle with the desktop config files, or with mimeinfo.cache or mimeapps.list?
Here is the content of the firefox-beta.desktop file I created:
[Desktop Entry] Name=Firefox Beta Exec=firefox-beta -P Beta -no-remote Icon=firefox Terminal=false X-MultipleArgs=false Type=Application StartupNotify=true StartupWMClass=Firefox Categories=GNOME;GTK;Network;WebBrowser; Comment[en_US]=Firefox Beta Channel MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;x-scheme-handler/chrome;video/webm; Name[en_US]=Firefox Beta [NewWindow Shortcut Group] Name=Open a New Window Exec=firefox-beta -new-window about:blank TargetEnvironment=Unity