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:
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:
``` 2.426:6844) : apparmor="DENIED" operation="mknod" class="file" profile= "snap.thunderbi rd.thunderbird" name="/ home/reinhold/ .Schreibtisch/ 3YM0sAtL. jpg.part" pid=13704 comm="thunderbi rd-bin" requested_mask="c" denied_mask="c" fsuid=1000 ouid=1000 8.060:6846) : 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.freedeskto p.UPower" member= "EnumerateDevic es" mask="send" name="org. freedesktop. UPower" pid=13704 label=" snap.thunderbir d.thunderbird" peer_pid=2041 peer_label= "unconfined" 7.854:6847) : pid=1750 uid=105 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor= "DENIED" operation= "dbus_signal" bus="system" path="/ org/freedesktop /login1" interface= "org.freedeskto p.login1. Manager" member="UserNew" name=":1.2" mask="receive" pid=13704 label=" snap.thunderbir d.thunderbird" peer_pid=1742 peer_label= "unconfined" 7.902:6848) : pid=1750 uid=105 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor= "DENIED" operation= "dbus_signal" bus="system" path="/ org/freedesktop /login1" interface= "org.freedeskto p.login1. Manager" member="SessionNew" name=":1.2" mask="receive" pid=13704 label=" snap.thunderbir d.thunderbird" peer_pid=1742 peer_label= "unconfined" 7.918:6849) : apparmor="DENIED" operation="open" class="file" profile= "snap.thunderbi rd.thunderbird" name="/etc/fstab" pid=13704 comm="thunderbi rd-bin" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0 7.922:6850) : apparmor="DENIED" operation="open" class="file" profile= "snap.thunderbi rd.thunderbird" name="/ run/mount/ utab" pid=13704 comm="thunderbi rd-bin" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[258976.048246] audit: type=1400 audit(171759162
[266201.656966] audit: type=1107 audit(171759884
[271081.412143] audit: type=1107 audit(171760372
[271081.459469] audit: type=1107 audit(171760372
[271081.473690] audit: type=1400 audit(171760372
[271081.479958] audit: type=1400 audit(171760372
```