My understanding is Doddy is correct
Linuxcnc needs the RT kernel
The link provided is for an iso of Linux mint 19.3 which also includes linuxcnc 2.8.0 already installed
This means that someone (beagle brain from memory) as already done the hard work and integrated linuxcnc into Linux mint

If I was John I would take the easy route abs use the iso with all of the hard work already done for you

Paul


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