On Debian 11 after apt upgrade from likely thunderbird:amd64
(1:91.13.0-1~deb11u1) to Thunderbird 102.3.0 (64-bit) i have seen some
visual changes in UI and e-mail content was not loaded, so i have
restarted TB and see that the unified Inbox (one folder for all e-mail
accounts inboxes) is missing some of the latest e-mails which i have
seen before TB restart. And indeed one of the mail accounts contains
these missing e-mails, but it is not displayed in unified inbox.
What helped: Right click unified Inbox folder and select Properties,
then "Select the folders to search" (Choose button), tick all, or just
all inboxes of all accounts.
Why it not missed before and now is missing?! I guess this is developer
failure that should be reported? I am guessing people will now
accidentally miss their e-mail thanks to this.