Comment 3 for bug 2067340

I'm also running into this problem, which appeared after the Ubuntu upgrade, which switched thunderbird from .deb to a snap package.
In the dmesg output I see several apparmor messages concerning thunderbird. I'm not sure which of them -- if any -- relates to the issue, but I strongly suspect that apparmor in connection with snap is to blame. I had similar issues when chromium switched to apparmor (they were solved in subsequent snap releases of chromium, though, mostly some pathes were missing in the whitelists). Here are the messages:

```
[258976.048246] audit: type=1400 audit(1717591622.426:6844): apparmor="DENIED" operation="mknod" class="file" profile="snap.thunderbird.thunderbird" name="/home/reinhold/.Schreibtisch/3YM0sAtL.jpg.part" pid=13704 comm="thunderbird-bin" requested_mask="c" denied_mask="c" fsuid=1000 ouid=1000
[266201.656966] audit: type=1107 audit(1717598848.060:6846): pid=1750 uid=105 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor="DENIED" operation="dbus_method_call" bus="system" path="/org/freedesktop/UPower" interface="org.freedesktop.UPower" member="EnumerateDevices" mask="send" name="org.freedesktop.UPower" pid=13704 label="snap.thunderbird.thunderbird" peer_pid=2041 peer_label="unconfined"
[271081.412143] audit: type=1107 audit(1717603727.854:6847): pid=1750 uid=105 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor="DENIED" operation="dbus_signal" bus="system" path="/org/freedesktop/login1" interface="org.freedesktop.login1.Manager" member="UserNew" name=":1.2" mask="receive" pid=13704 label="snap.thunderbird.thunderbird" peer_pid=1742 peer_label="unconfined"
[271081.459469] audit: type=1107 audit(1717603727.902:6848): pid=1750 uid=105 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor="DENIED" operation="dbus_signal" bus="system" path="/org/freedesktop/login1" interface="org.freedesktop.login1.Manager" member="SessionNew" name=":1.2" mask="receive" pid=13704 label="snap.thunderbird.thunderbird" peer_pid=1742 peer_label="unconfined"
[271081.473690] audit: type=1400 audit(1717603727.918:6849): apparmor="DENIED" operation="open" class="file" profile="snap.thunderbird.thunderbird" name="/etc/fstab" pid=13704 comm="thunderbird-bin" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[271081.479958] audit: type=1400 audit(1717603727.922:6850): apparmor="DENIED" operation="open" class="file" profile="snap.thunderbird.thunderbird" name="/run/mount/utab" pid=13704 comm="thunderbird-bin" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
```