Here's another vote for the older Mini with the external power supply. No fans. Stays cool all the time . . . and silent. I sure wish Apple would make these again.
I would say terrible things about those that hate the brick.
But I won't.
I do wish we had a nice 110 watt brick.
The restrictions caused by the internal psu are pretty bad.
And you need a power cord anyway so find a way to hide the brick.
But thats apple classic form over function bs.
your choice for a headless mac is still mac mini vs mac pro or 600 usd vs 3000 usd.
The iMac is pretty but worthless as a HT .
But thats right who needs HT with a 60 inch 4k screen when you can watch a movie on your iPhone or iPad.