No it's not possible. If you plug your monitor into the mobo then that monitor will be driven by the iGPU. No way around it. You can buy an HDMI to VGA active adapter like this https://www.amazon.ca/Cable-Matters-Active-Female-Adapter/dp/B007SM7O2U
EDIT: Oh yeah if you have DVI you can go HDMI to DVI
Yes, an HDMI port will work if you buy a monitor with an HDMI in (typically slightly more expensive). You could also buy an adapter like this one to adapt to VGA or DVI or something.
Your computer can't handle DUAL monitors, but one extra monitor should be no problem. Almost every laptop can handle a single external monitor without any issues, it's when you have multiple that you have issues.
I believe he used a rx470/480. But now that I think of it he also needed an active adapter like this
Believe it or not, HDMI adapters work pretty well. I have one of these for my laptop and it works a treat.