

In the subject you wrote “successful full sys update” but the script and the other suggestions I see so far don’t actually handle the “successful” part.
The log message only tells you that the update was started and the db mtime only indicates that the db was touched without saying anything about success.
I’d go about this by always performing the updates through a wrapper script that could check the exit status of the pacman or yay command and record a timestamp accordingly.
Not sure what’s causing the UI issues but another way to go about this is to create a custom collection and configure your browser to use it. This way you can control what shows up in “recommended”. IIRC you have to use nightly, beta or a custom build like Fennec to allow using a custom collection.
instructions for managing collections
making FF user a custom collection
collections web UI