By creating a backup from the .Thunderbird in Ubuntu 22.10 LTS i've got a failure "datasystem does not serve symbolic links". The file "lock" in dkfjslf.default couldn't be copied. I think, it will not be a problem, but it ist irritäting to get such a message, and it isn't named in the help files on this website. By the way, there is no chapter about backups. so it is difficult to find any articles about that.