I want to shout out this awesome project.
https://github.com/Macjutsu/super
I've been beating a dead horse trying to figure out a way to keep the new M1s updated with little to no user interaction, not let them be able to access the Software Update portion of the settings panel since, let's admit it, end users are going to click on the shiny new OS Upgrade and not the tiny blue button all the way down at the bottom.
I was able to set this up in a day and configure all settings and testing has been amazing.
It only downloads the updates and not any upgrades, unless specified in the configuration, BEFORE prompting the user for a restart so it's 99% transparent to the end user, let's me setup deferment time and amount, custom branding to make sure it looks authentic to users, auto updates things like Safari that don't need a restart to update, and most importantly can authenticate as an admin account with a secure token instead of needing the user to be a volume owner!
If you're looking to keep your devices on their current OS for the next few years and just want updates to work and ACTUALLY have some kind of administrative control over updates. You have to check it out.