I found this:
https://github.com/nextcloud/server/blob/master/lib/private/Notification/Manager.php
starting at line 313:
...
// TODO Remove time check after 1st March 2022
$isFairUse = $this->timeFactory->getTime() < 1646089200
|| $this->subscription->delegateHasValidSubscription()
|| $this->userManager->countSeenUsers() < 5000;
...
I have increased the “countSeenUsers” value. The message is gone. But this was a little bit insidious.
best regards