NAUI, SEI, PDIC, and NASE have master diver programs that are not recognition for having a bunch of cards. They are stand-alone courses with Instructor level knowledge and skill requirements minus the teaching component.
That said, it's going to be the instructor that makes the course and it should be a course you can fail if you're not willing to put in the work. Before I went inactive with SEI the last Master Diver course I taught was one student and it took him 6 months to complete to my satisfaction.
Several pool sessions, even though he was rescue certed by me and had taken AOW and UW Nav as well, roughly 20 additional dives, and some free diving skills.
Course fee was 600 bucks but he spent at least that on travel, fills, lodging, etc. by the time we were done.
He went on to DM later with another agency and breezed through that.
The minimum standards for the courses are not overly impressive as written. But a good instructor will throw as much as you can handle and a bit more at you to make sure you are worth giving the card to.
I also recommend to anyone considering the DM route to take at least one good tech course first to get a dose of reality that is missing from many recreational paths. I didn't and as a result, found out the hard way when I did get some tech training that I had a poor understanding of much of what diving at higher levels is about.
A good tech course will tell you the risks that some recreational programs seem to gloss over or minimize in favor of the sun, fun, and new people line of BS. A DM class will not make you a better diver. You should be an excellent diver before starting it. I've seen DM's I wouldn't get in the pool with.