I use Thunderbird on Ubuntu for emailing, emails are saved locally. I bought a new computer, installed Ubuntu and would like to transfer my email account including all the old emails to the new computer, old and new are Ubuntu with Thunderbird.
There are instructions on how to migrate, for example here although that is for windows systems. I tried to adapt that and copied everything from the xxxxxxxx.default folder which contains the profile to the new laptop. This aparently wrecks the Thunderbird installation. On starting Thunderbird, after a few seconds I get a popup that Thunderbird stops responding, offering me to either force-quit or wait. If I wait I just get the popup again after a few seconds. I deinstalled Thunderbird and tried the copying over the folder again and got the same result.
What is the proper way to migrate my emails to a new computer?
Extra info after comments: the old install is a Ubuntu 22 version with traditional APT, the new one is a Ubuntu 24 version with snap.