.Net Framework 4.7.2 does not want to install on my laptop because of certificate trust issues? Now what?

Given that .Net Framework is A) made by Microsoft and B) given you didn't say Linux, you're probably using Windows, and C) Master of Magic is a DOS game, that is very odd.

It's probably used by Caster of Magic? anyway, try downloading from official sources? Also do a Windows integrity/DISM check? You can find out how on the internet; I just know how to follow the instructions I find. :)

It's required by the Slitherine launcher and installer. All game versions are playable without it. The easiest workaround is to install on a machine that can and then copy over the game files. However, do note that the DOS versions may require some manual setup in this case (for DOSBox).

Check my post:

https://www.gog.com/forum/master_of_magic/for_those_who_have_the_net_framework_472_problem

Hope it helps :)