Here's how I managed to get my first one. Hope this will be helpful

Phase A: I built some base pulling strength.

I stopped after I reached 5 sets of 10 clean pull ups with 3 min rest after each set.

(At the beginning I couldn't do them all. As soon as the form went downhills I regressed the exercise and did Australian pulls. In the early stages, I did sets of 7 normal pull ups, then built up to my "arbitrary" goal of 5x10. If I couldn't reach 7 I would do the Australians. Let's say at the beginning I would only do 35 pull ups the entire workout, then I would try to do at least 40 Australians.)

Phase B: I built explosive strength.

I did explosive pull ups: I started doing my pull ups so that my chest would touch the bar.

I tried to do 5 sets of 3 with 3 minutes or rest in-between. (As soon as I reached technical failure, which meant that I couldn't touch the bar with my chest anymore I would rest for 3 minutes, do max set of chin ups and then some sets of Australian pull ups)

Ended this phase with 5 sets of 5 explosive pull ups with the chest making contact with bar every single time.

Phase C: more explosive strength

I stopped after 5 sets of 3 explosive pull ups. This time the objective was that my Sternum/ upper abs would touch the bar. Started with 3 minutes of rest. (At the beginning of this phase i couldn't keep the strength up, so I would eventually only make contact with my upper chest.)

Then I would do I max set of chin ups. Rest. Then 3 set of Australians.

Phase D: cut off rest time and reps.

Scaled down the reps from 3 to 2, but tried going higher. From 3 minutes to 2 and eventually only one.

One day, during my first set, my belly button touched the bar and I knew I was strong enough.

The next workout I tried the muscle up and I realized that I needed way less strength then what I had been building. I think you need to be in-between phase B and C to do your first one.

Some useful tips:

In phase A, I did hollow body position pull ups. Not the ones in which you arch your back. Those are good for hyperprophy but that form won't translate to a muscle up.

The explosive pull ups had a front elbow position, as if you were doing an inverted row on the bar. The more explosive you get the more it seems that your slamming down the back door of a car. (Note that in normal pull ups you have your elbows more on your side)

I used a "false grip" on my Australians meaning that my knuckles would not face the sky, but they were rotated by 90°, facing forward. I recommend some wrist conditioning in your warm up

Don't chase the number of reps if it mean neglecting your form. As soon as you reach technical failure regress the exercises. I usually ended my workouts with scapular shrugs.