So bummed out that I wrecked the HDMI out on my MiSTer. I was trying to figure out a new monitor layout and unplugged/plugged it in a few times. I could SSH into it no problem, but no HDMI out. After peeking around on the forums, turns out that the MiSTer doesn't take kindly to that while it's still on-- I forget the technical reason. Oh well. Many, many hours of fun playing games with my son on the it, I got my money's worth.
Dunno which variant you bought, but the QMTech mister clones on Ali Express are affordable, work perfectly well, and come with the expanded 128MB SDRAM expansion and analog I/O board bundled up in a convenient case. I have 2 of them, along with the MiSTer Pi, and I'll probably pick up a couple more for dedicated applicaitons (3d-printed retro computer workstation, Normal/TATE mode cab builds, and a couple just to hook up to the CRTs I have lying around).