It was mentioned on a video that Austin wrote a machine based program for those that are afraid, or are otherwise unwilling, to train with barbells. My Dad is in that category. Though he will likely never lift with free weights, he will go to the gym twice a week (inconsistently) and do machine work. I don’t actually know what he does, but I assume light weight, 1-3 sets, 8-12 reps.
I was curious, what does an effective machine based program look like? If I were to write one, I would make an effort to progressively overload each movement, over time, in either load or volume. Rep and set scheme would be 3-5 sets, 5-12 reps, generally sticking to RPE 7-8.
It could be as simple as a program of leg presses, machine chest & shoulder presses, and machine / cable rows & lat pulldowns to cover the “big” targets. I think 3-5 sets of 5-10 reps at that RPE target, assuming progressive loading over time, would probably work fine for your Dad’s purposes in this situation.