I'm still running Ubuntu MATE 22.04.5 LTS. Yeah, yeah, I'm planning to move to the latest LTS release any day now...
But nearly every day for the past week of so I've been getting updates. Many of these are kernel, headers, and systemwide updates. Each requires a reboot. Not that it inconveniences me, but I don't remember the last time such a flood of updates was being sent downstream. What's up with that? Kernel bugs, or just standard "getting ready for the new year" stuff?
It might be worth checking the change logs if you know the package name(s). Either viewed locally from /usr/share/doc/<package>/, online at packages.ubuntu.com or with Synaptic / Software Updater.
They'll usually describe what changed for packaging purposes, it might be a patch, bug fix, security. Some packages (kernels in particular) might just reference an "upstream" version, of which case the answers are there in the repository's (source code) commit history if you felt like doing some digging.
I'm not too familiar with this Git interface, but this might be 22.04.x kernel - as an example of the changelog file for 5.15.0-154.164:
Once a week (monday my local time) I'm reviewing the weekly list of updates for each supported release for Ubuntu News, and there are times when I note (and sometimes comment in a team room) that a list is larger/smaller than expected, or usually something that feels unusual. The lists do vary in size though at specific times of the year.
If you're worried you received upgrades that you shouldn't have, contrast what your box received with one of the many lists of what is provided.
The list of updates is just packages updated (SRU'd) which is made for each release; though as always many problems (CVE's etc) impact multiple releases so the one cause can appear in multiple lists as each of the lists is specific to a single release.
What you receive updates for is package specific; if you have that package installed & have correct sources for it; you'll receive the updated package from -security or -updates, but you'll see it on the list.
Have you explored any of the list of updates ? (The Ubuntu SRU/Release/kernel.. teams recently blogged about their December & January intentions anyway; so notice of what was happening & what to expect was given)
This reply is purposely generic as Ubuntu-MATE 22.04 LTS is EOL