We can buy split system air-con from hardware stores here. Finding a right fitter that isn't too much a grumble bum is the key. A couple of them that I've fitted, my usual air-con guy refused to come out. "i;m too busy, can't you just do it?" They come with enough refrig charge in them if your frig lines are short ie though a wall. And they have a air bleed so you just do that after checking the plumbing.
My bloke says that the problem with the consumer buying the stuff is they buy the cheapest system without considering the extreme hot/cold days. It's just one or two people who buy the wrong damn thing, then complain to the regulator who then is forced to spoil the fun for everybody.
I've put in several split systems, some heat pumps some straight AC, several furnaces and one mini split, 100% success rate on all of it, all but the mini split were more than 15 years ago and every one of them I put in is still working. I figured it out just fine on my own, but I had to get the stuff from various ebay sellers, mostly scratch & dent equipment. Built some of the tools like my refrigerant recovery machine myself. Already had a good vacuum pump and all the plumbing and electrical tools.
Yes a lot of people are going to buy the wrong thing or screw up the install, that's their problem and their money, just like any other DIY project. The HVAC guys have every right to refuse to come fix botched installs if they don't need the money and I don't mind if the vendors won't warranty the DIY stuff if they'd just sell it. I put in that mini split recently because my friend got quoted almost $8k to have one put in and he found he could buy exactly the same system online for around $2k. No warranty for a DIY install but he realized we could screw it up, throw it away, buy a whole new system and try again and still come out way ahead and it was a good excuse to hang out and work on a project. Piece of cake, knocked out the whole job in an afternoon and it sailed through a record breaking heat wave about a month later.
I don't need technical help, I don't need support, I don't need to ask questions, I'd be happy if I could just walk up to the trade counters, ask for what I want, pay and walk out, same as I do at the electrical and plumbing places when I need something I can't get from the big box stores.