This sounds very much like bug #1945741, which was an upstream bug (https://bugzilla.mozilla.org/show_bug.cgi?id=1734428), but was marked as fixed 9 months ago. So it's probably a slightly different variation of that bug. Would you mind filing a new bug report at https://bugzilla.mozilla.org/enter_bug.cgi?product=Thunderbird, mentioning that other upstream bug, and sharing the link to it here?
** Bug watch added: Mozilla Bugzilla #1734428 https://bugzilla.mozilla.org/show_bug.cgi?id=1734428 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to thunderbird in Ubuntu. https://bugs.launchpad.net/bugs/1981163 Title: In Compose window, if a PDf is joined and clicked to open, Thunderbird launches Firefox instead of Evince Status in thunderbird package in Ubuntu: New Bug description: In Thunderbird on Ubuntu Gnome, I set Evince as default program to open pdf files from Thunderbird. In received messages, and those saved on "Sent" folder, it works perfectly. But in the "Compose" window: if I add a pdf file to the message, and double-click on it to open and verify it, Thunderbird always uses Firefox to show it. In case Firefox is not installed (has been removed), I have an error message telling there is not associated application for pdf files and to go to Preferences - where Evince is already and still defined as default. It happens since many months and bug is still present in Thunderbird 102 / Ubuntu 22.10 beta. It's not the same as bug 234349 as here, it's not an URL file but directly a pdf joined in a mail. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1981163/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
