Updates get published at various sites, so why not monitor such a site.
I work with the Ubuntu Weekly Newsletter, the last issue UWN #633 has a very clear
No activity this period.
mutter update was listed for that week for
focal/20.04, but if you don't have
mutter installed you won't have had that updated package.
There were many more the week before (UWN #622), but you can check yourself (it's a weekly publication, and you know your release)
The latest release usually has the most updates (that's groovy/20.10, of course ignoring development/hirsute). Older stable releases get fewer generally (only back-ported security updates)
If it worries you, you can always scan the Ubuntu Weekly Newsletter at the Ubuntu Fridge / UbuntuForums / wiki & other places where it's posted.
In the end, we all need to check it ourselves, as we tend to change the packages we have installed (you will also know your release, as you didn't say - I don't know it, so used focal as example as it was the release of another question).
I'm using Ubuntu Weekly Newsletter as example of a place you can check, selecting it because it's one I'm very aware of being involved with it since 2015, but it's not the only source for such information.