Android 16/OneUI 8 (Samsung): New Mail notifications not happening/erratic

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

Thunderbird for Android

App version

11.0b5

Where did you get the app from?

Google Play

Android version

Android 16 and One UI 8

Device model

Samsung Galaxy Flip Z 7

Steps to reproduce

Set up TBird with default install, add an account. (I have 3 Gmail and 2 IMAP). Use normal polling for new Mail check, not push. Close the phone (which locks it). Send new Mail to the account from some other system.

Expected behavior

The cover screen (and lock screen when phone is open) should show a new mail envelope notification. This worked on a Z Flip 5 running Android 15 and One UI 7. Other applications have their notifications appearing during this time.

Actual behavior

No new mail notification appears for quite some time with the screen closed (sometimes never, sometimes hours). Even opening the TBird app after unlocking the phone will sometimes not show a notification until forcing a mail check manually - then notifications will appear as expected for current email. Closing the phone again will suspend the notifications.

Logs

Just upgraded from A15/OneUI 7 to A16/OneUI 8. was running TB 11.0b5 on the old system, and notifications worked as expected with the phone closed. On the A16/OneUI 8 system the notifications are not appearing as they did - sometimes missing entirely. I also am running 11.0b5 on a Pixel Tablet with "pure" Android 16, and notifications show on the lock screen as expected.

Start by reproducing the report on a Samsung Galaxy Flip Z 7 with Android 16, One UI 8, Thunderbird 11.0b5, a locked phone, and normal polling. Compare behavior with the reported Pixel Tablet and Android 15/One UI 7 setup; done means new-mail notifications reliably appear on the cover or lock screen while the phone is locked.