In my state they require:
>160 hours of education/vocational training and 2 years’ verifiable experience in the trade
To get the license to install minisplits (two years experience generally means working an apprenticeship).
It's no wonder install costs are so much in the US. And as you've experienced, they're hardly rocket science to install. The 160 hours training would be more than enough, I'm not sure why 2 years experience gets tacked on the end.
Unless your state is very unusual that is the requirement for installing them for other people as a tradesman. In most states if you are DIY for yourself all you legally need are the electrical permits for the wiring hookup (which for DIY don't require that "apprenticeship").
Thankfully, the training is only required if you're doing the installs for/as a business.
What will they do if they learn you installed your minisplit yourself?
This kind of thing is right up there with calling dig safe before a project that will be exclusively hand excavated. At some point you're basically just paying to circle jerk it with the other boot lickers in the office or at the cocktail party over how much you paid for no reason just because the rules that will never be enforced say you ought to.
Protection racket. They guys doing the installs now would make much less money if just anyone with some tools could start competing with them.