Black Screen after install, not detecting 2nd monitor, cannot use 1st

Evening, folks.
I am having a pretty critical issue with my laptop after installing Win 10 for the first time. It seems like it is not detecting my second HDMI monitor. I did see that this was an issue previously resolved, but my predicament is a bit different. I use my second monitor as the primary due to the laptop monitor not working. As it is, I have been sitting for close to an hour on a black screen due to my main monitor not being picked up and no way to visually walk through to make it my primary again... If that is even the only problem. Are there any ways I can switch to my main monitor (2nd monitor) worth no visual representation whatsoever? Hope I can get some assistance on the issue as this has rendered me computerless for the time being.
(Typing from my phone, so excuse the awkwardness of my writing. :) )

HI and welcome to the forum! :)

Ohh, that is an annoying issue...
If this happened to me inside Windows, I would try the usual keyboard combinations, which should switch the output device. E.g. on my make and model it would be Fn + F5, I believe. It may be different for you though. Maybe the manual or a search on the internet will tell you, what this combination is for your PC.

Another idea might be to use a different monitor: Old and VGA should basically always work.

Another aspect is: For these shortcuts to work, your keyboard must have been detected properly. Most likely it has been, however, there are a few cases, where people had problems with this Fn stuff after the upgrade. Also I don't know, where exactly in the installation process you are... In the worst case, which I don't know whether it's the case or not, such Fn stuff maybe generally is not working there, even if the keyboard got detected correctly.

As a last resort, maybe it would be an idea to look at a YouTube video to find out, where in the install you have to hit which buttons and to use the keyboard to do that blindly?

Thanks for the response!
Sadly, none of the Function commands seem to issue a response. I also wish I knew where I was in the installation process. Finally up and got the courage to power the laptop down late last night. A friend of mine told me that this is a known issue with NVIDIA cards; that is, only being able to use one monitor at a time. Maybe trying different monitors will do the trick. I'm half tempted to crack the thing open and manually unplug the laptop monitor from the inside... Thankfully, I'm not that desperate. Yet. :)