interface of my mac os in the mac mini m2 is slow due to the external monitor

HDMI is great for TVs and such, not so great for high res displays.

I would use a USB-C to DisplayPort cable from the Mac mini to the NPC instead of HDMI.

for example > https://www.amazon.com/dp/B08B3SB5VC/ref=sspa_dk_detail_4?

What external monitor(s) and what type of cable connection are you using...?

Chrome is a huge resource hog. What happens if you ditch Chrome and use Safari...?

Maybe in Activity Monitor, highlight it then click on the tiny i icon to get to the Sample button to see if we can catch it there.

Let's see if we can track down the usage, get Task Explorer, it's only using 1.7% on my2019 Imac running3 browsers with lots of Windows & tabs open, as well as more than a dozen other Apps....

https://objective-see.org/products/taskexplorer.html

I could do a lot of guessing but using Brave could be considered a diagnostic to help eliminate things or not.

Everything uses Window Server, Finder, Browsers, practically everything to do with the GUI.

Could be, quit Chrome & see how far it drops.

Might try this, it's Chrome Browser without google & without Ads...

https://brave.com/

Uses less resources than Chrome.

For a bit after a reboot, restart, whatever, I would expect Windowserver to be elevated then drop off cpu% wise.

As for task explorer be able to help, try going through the files list in Activity Monitor. like SubmitDiagInfo for instance to se if we find a big CPU%.

Right now I'm mulling a borked Install or a Hardware issue.

HDMI wasn't invented to help us, but to protect content providers, I agree with den.thed.