munki VS nudge

In the non-MDM tool space, look into Munki https://www.munki.org/munki/

this experience is an indication that the opco didn't hire the right expertise. If the numbers you quoted ie 30k desktops, 50k total were not macs, it's clear that the org didn't have the kind of mac experience needed to manage a a new org with all macs.

It's entirely possible for administration of macs.

Start networking/asking around with places like Disney or Pixar, etc which have a large amount of graphic artists using macs. For example, from Disney https://github.com/munki/munki gets you to a certain point.

Other tools like Kandji (lightweight) and the 900 lb gorilla in the industry Jamf gets you the other management / administration bits needed

If this opco that you referred to never got a Jamf rep to work with them and to try out their (yes, very expensive) products, then this is mostly inexperience with the mac ecosystem.

There's a decent open source option: https://github.com/munki/munki

I got to use it at work at Meta (as end user), and it seemed to work quite well. They delivered Android SDKs/IDEs and a bunch of other things that I'd personally install through Brew with Munki.

Munki is not an MDM and I recently learned there's this project called Installomator that might help.

Or Munki

This is a feature of munki called default manifest resolution. Though I prefer to avoid this and explicitly set the client identifier for all devices.

another option is munki https://github.com/munki/munki, for the software update part,

Nudge https://github.com/macadmins/nudge

Not a direct answer but I've been implementing Nudge all day. It reminds the user to update. You install the pkg and then push an mdm profile with your minimum version and date. https://github.com/macadmins/nudge

We deployed Nudge to our Macs to remind users to accept their updates. There's a script on Microsoft's Shell script GitHub to deploy it/keep it up to date. You can build a custom config profile using the documentation on the Macadmins' Nudge Github home as well.

Nudge: https://github.com/macadmins/nudge

Taking a few steps back, I’m assuming this is in an effort to patch macOS? If so, I personally feel this is not the right method. Take a look at other encouragement tools instead, like Nudge (https://github.com/macadmins/nudge) or utilising device compliance solutions like Jamf and Intune via their plugin solution.