If you want to get rid of shine you just need to get the grease off the leather.
I use All Purpose Cleaner on leather seats, or if really old and looking seriously hard and shiny I will use engine degreaser or even a magic eraser.
All purpose cleaner I mix 5:1 with warm water, engine degreaser around 4:1.
Soft brush and work it gently, it will come up looking like new.
All car leather is spray painted anyway, then it has a top coat to seal it and give it some protection. When it goes hard and shiny it is a build up of grease, normally dead skin and body fluids. Nice!
You just need to get this layer off the top coat, which has a matte finish to it.
This is a bolster off a 15 year old E Class with 120,000 miles on it, it was that typical rack hard, shiny looking leather, an hour or two with some all purpose cleaner and a Meguire's interior brush and they came out looking great.
I would never put conditioner or leather feed on any type of car leather, because of the top coat all it is doing is adding another layer of gunk on the top, it may look great for a couple of weeks, but then it will start to shine up again. The answer is to keep the grease off, and a £2 All Purpose Cleaner or Engine Degreaser will do that as good as anything out there.
If it is really bad, you can use a magic eraser, however, make sure it is kept very wet and be very gentle, think of it as a very fine sandpaper. Do a small section at a time and keep looking at the eraser to make sure there is no colour/paint/dye coming off.
A magic eraser on your steering wheel is a good way to try it out and see how well it works, it will get the hardest, shiniest of steering wheels looking and feeling factory new again. Again, make sure it is wet, and be gentle, 3 or 4 light wiper overs is best, the moment it looks matte, stop.
This was a 3 series I did a few weeks back, 13 years old and again the leather was horrible, steering wheel was nasty.
It looked more like a year old car when finished.