It's an issue with the actual ports. And again it's not limited to just the Mac mini as my Dell Micro does the same thing. I  have personally tried many different HDMI-HDMI cables from the ones that came with my HP and Acer monitors  along with many different brands of quality HDMI cables.
I am using HDMI to DisplayPort cables with my Dell since that is all it has. But the monitors still blank out just like the Acer and HP monitors on my 2018 and M4 Mini's when using HDMI-HDMI cables.
No amount of swapping cables helps. The only thing that helps with the Mini's and the Dell Optiplex Micro is using HDMI - USBc cables.