NOTE: This still works, but see update below
Mozilla Thunderbird is still my favorite desktop mail client (and, despite what you may have heard to the contrary, is still in active development by its user community), whereas Evolution is not. Unfortunately the Gnome developers have not provided any obvious way of designating Thunderbird’s Lightning calendar as the default in place of Evolution.
In order to get Thunderbird in the drop down list in Gnome’s Settings… Details… Default Applications… Calendar you need to edit the mozilla-thunderbird.desktop profile under /usr/share/applications by appending some text to the MimeType-message line:
The added text is “text/calendar;text/x-vcard”.
Once the change is made you need to make Gnome recognize it with the update-desktop-database command, issued as root:
Once that’s done Thunderbird will show up in the list and can be selected.
Update: Added the “as root” qualifier to the instruction to invoke update-desktop-database. Only running it as my user didn’t work for me with the latest release of Fedora (“Twenty Three”).
As always with Gnome, YMMVFRTRWW (“Your Mileage May Vary From Release to Release Without Warning”).