I am running Thunderbird 91.5.0. on two identical operating systems, i.e. Ubuntu 20.04, the one a desktop and the other a laptop. When we travel, I transfer my .thunderbird profile folder to my laptop so I can access my mails, diary etc., however, since the latest Thunderbird upgrade to 91.5.0 the laptop no longer recognises the .thunderbird profile generated on the desktop computer. The problem started when the laptop installation was still running on the old Thunderbird version, so I hoped and assumed that if I upgrade to the same 91.5.0 version on the laptop, the problem will be solved, but that is unfortunately not the case. When I copy the .thunderbird file to my external drive, there are some files that cannot be copied. The error message reads "Error while copying 'lock'" and "Filesystem does not support symbolic links" - Could this be the reason and what can I do to resolve the issue?