Getting a Mac to stop stuttering when using HDMI

My target is an Intel Mac-mini using a TV as the monitor. I'm trying this approach as MacOS updates are not available any longer.

Zorin loads and runs OK, but the audio stutters badly. I've followed the guide at GitHub - flagsoft/How-to-make-Linux-audio-sound-working-on-Mac-Hardware: How to make Linux audio sound working on Mac Hardware to install a kernel module for the audio hardware but it's made no difference.

Any ideas?