I recommend this approach: everything in the profile is captured: settings, passwords, accounts, messages

1. start thunderbird on old PC
2. click tools>export and then click 'open profile folder'
3. exit thunderbird
4. copy profile content to external media
5. install thunderbird on new pc, downloaded from thunderbird.net
6. in receiving PC, click help>troubleshootinginformation
7. scroll to 'profile folder' and click 'open folder'
8. exit thunderbird
9. now, paste contents of exported profile, overlaying contents of profile.
10. if there is a compatibilitie.ini file, delete it
11. restart thunderbird

TIP: if IMAP accounts that have HUGE message folders, you can delete the message folders prior to the copy and they will be recreated on new PC. (Do the DELETE in profile when Thunderbird NOT RUNNING, e.g. imapmail\<IMAPaccount>\inbox

I just went with the export. Synced it with nextcloud and on the new machine in thunderbird go to hamburge/tools/import (a bit tricky as it starts with attempts to create a new account)

The import worked like a breeze:

• Asked for pw for all accounts
• Started oath2 for google, yahoo and microsoft accounts.

What does not work is OpenPGP keys.

This key could not be found! If you want to use it you must import it to Thunderbird ''

They are not part of the export. Which is a bit silly as those are the most tricky part of moving. I understand the reason. but tricky none the less (now where have a i put me private keys …🤔

IMAP mails are not part of the export. That is not clear in the UI.