> Plugging a monitor enabled the dedicated GPU.
There's the problem.
Dedicated NVidia and AMD GPUs are the cause of a solid 50% of issues or instability with laptops. Including for Apple.
I get that some people really need them, but having one built-in to your laptop is just begging to have way more problems than if you left it out. If you want/need a high-reliability machine and can afford not to have a dedicated GPU, leaving it out is a really great way to instantly improve your odds a ton. Integrated GPUs used to be so bad they were a liability even if you weren't a gamer, but that hasn't been true in a long time. Hell, my base-model-with-a-little-extra-memory 2014 MBP could play Minecraft at high settings and Kerbal Space Program just fine on the integrated Intel GPU, plus a bunch of other Unity games. I know those games don't exactly represent the cutting edge of graphics (and didn't back then, either) but it was surprisingly capable.
Actually, now that I think about it, at least for me personally, GPUs are probably the cause of about half my problems on desktops, too.
