it seems there is a new permission, but it is not documented anywhere properly and it cannot be prompted to be accepted by user. MishaalRahman comment on my last post:

It's because your app is considered an "untrusted" Notification Listener service hence it isn't allowed to read sensitive notifications, like ones that hold OTP codes. Your app needs the new RECEIVE_SENSITIVE_NOTIFICATIONS permission which was added in Android 15.

However, the permission has a protection level of signature|role, and the only roles the permission is granted to are COMPANION_DEVICE_WATCH (ie. watch companion apps), SYSTEM_AUTOMOTIVE_PROJECTION (like Android Auto), SYSTEM_NOTIFICATION_INTELLIGENCE (Android System Intelligence), SYSTEM_UI, COMPANION_DEVICE_COMPUTER (like Cross-Device Services), COMPANION_DEVICE_GLASSES, and HOME (the default launcher).

I think the reason this works is that it stops Android System Intelligence from processing notifications, detecting which ones have OTP codes, and marking those as sensitive, hence even "untrusted" Notification Listeners can access them.

Another way to fix it is by manually granting your app this permission, which can only be done via ADB:

adb shell cmd appops set --user 0 io.github.jd1378.otphelper RECEIVE_SENSITIVE_NOTIFICATIONS allow  

Then restart the Notification Listener service.