Since the latest major update I cannot see sender and subject in the notifications anymore. I only see the mail account name and the number of new mails. First I thought I see this only when I have more than one mail and K-9 Mail just groups them. But it’s also when there is only one new mail. I checked all settings within K-9 Mail and in the notification settings of that app in the operating system, everything seems OK. I use Andoid 9 on a Samsung Galaxy S8+.
Is this a new “feature” or is there a setting I did not find yet?
Try setting Settings > General settings > Notifications > Lock Screen Notifications to Same as when screen unlocked. It’s quite possible the lock screen “detection” is not working properly on your device and only notifications with reduced information are created.
Fixing problems with notifications is the next big item on the roadmap.