Removing the configuration directory (mv ~/.thunderbird{,-prev}) and configuring from scratch gives a working Thunderbird. Presume this problem is caused by the Ubuntu 20.04 to 20.10 upgrade. (Thunderbird worked before the upgrade, but not after it!]
Removing the configuration directory (mv ~/.thunderbird{ ,-prev} ) and configuring from scratch gives a working Thunderbird. Presume this problem is caused by the Ubuntu 20.04 to 20.10 upgrade. (Thunderbird worked before the upgrade, but not after it!]