I see this issue in 20.04 but it interfere with starting thunderbird. I'm using en-US.
jlquinn@cerberus:~/Videos/summits$ lsb_release -a; uname -a; apt-cache policy thunderbird No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 20.04.2 LTS Release: 20.04 Codename: focal Linux cerberus 5.4.0-80-generic #90-Ubuntu SMP Fri Jul 9 22:49:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux thunderbird: Installed: 1:78.11.0+build1-0ubuntu0.20.04.2 Candidate: 1:78.11.0+build1-0ubuntu0.20.04.2 Version table: *** 1:78.11.0+build1-0ubuntu0.20.04.2 500 500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages 500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages 100 /var/lib/dpkg/status 1:68.7.0+build1-0ubuntu2 500 500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1901829 Title: thunderbird fails to open, xml parse error To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1901829/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs