I mean, even if just installing a different OS were an option, you’d need to install and setup that OS on a few hundred computers or more. I used to work for a place that would essentially do the enterprise enrollment in bulk before shipping off the computers to schools. I could only setup a bit under 100 over an 8 hour workday, assuming no major issues (like captchas on the login step, or the wifi going out). Keep in mind that we also had specialized little microcontroller* USBs specifically for doing all the enrollment keypresses, and enough of those for someone to setup multiple computers at once.

I am actually curious as to how you would make a locked down managed linux OS akin to ChromeOS. Maybe there would be a way to do something like that that’s also faster to setup, but idk.

*centipedes are the name for the ones we used.

Assuming you’re using the default Ubuntu (the one with Gnome), it’s under the display settings and called night light.