Comment 7 for bug 1899667

I can confirm Robert's message : on Ubuntu 20.04 default gnome install, it doesn't attach a file.
And the proposed apparmor "fix" + set to thunderbird did the trick.

Alsos note that if using "Ubuntu live" from an USB key, with a correctly setup thunderbird, the composer windows of thunderbird does include the file when used from libreoffice's "send file/pdf per email"