I find the option to enable push notifications for folders (I guess IMAP IDLE?) a bit tricky to locate in Thunderbird.
Most mail clients I’ve used use IDLE by default if it’s supported, so a user switching to Thunderbird could expect to be notified of new emails instantly as well, and could be disappointed when that doesn’t happen.
I think the following would be good options to improve on that:
Personally, it took me quite a while to figure this out. I kept looking through Account Settings > Fetching Mail, suspecting either my configuration was broken or I’d missed the option. Eventually, after some skimming through GitHub issues, I discovered that the setting is actually in the side pane under Manage Folders for each account.