Unfortunately this doesn't seem to work to make Thunderbird open links in a particular Firefox profile due to this 21 year old bug: https://bugzilla.mozilla.org

Unfortunately this doesn't seem to work to make Thunderbird open links in a particular Firefox profile due to this 21 year old bug: https://bugzilla.mozilla.org/show_bug.cgi?id=216252 https://bugzilla.mozilla.org/show_bug.cgi?id=216252.