Comment 2 for bug 1877427

Thank you for your bug report, I can't confirm the issue on a standard imap folder clicking on a discussion, the last message is opened correctly and the first one only one. Do you get any warning on the console if your start thunderbird there?

Could you give some details on the type of account you are using?

Note that there is also a snap which is using the upstream provided binary if you want to test if that has the problem?
$ snap install --beta thunderbird