When I try to download/save files/attachments from Firefox/Thunderbird, I get a 0 byte file in my Downloads directory.
I have tried all possible permissions but no difference. In both cases, it works if I save to a folder outside my home directory (eg /tmp/downloads/) with the right permissions. My home directory is encrypted with fscrypt, not sure if this could be the issue.
This is on a fresh Disco minimal install. Firefox pre-installed, Thunderbird installed from default repositories. This issue doesn't affect any other programs.
Posted a bug report here but seems possibly not a bug: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1828011