Maybe it's just me, but I think the proliferation of mechanical keyboards brings people closer to the fringe where custom keyboards, layouts, parts and pcbs are the norm for the pursuit of perfection.
The Dygma Defy has also been making waves, it released not too long ago. [1]
The Keyboardio Model 100 has been out for a while, it pops up occasionally on eBay so can't be too unpopular if it shows up there. [2]
The MoErgo is probably less well known but has a good following both in the US and Europe. [3] Their Discord is pretty active.
> premium to kinesis for their garbage software
All the keyboards above are programmable, often with more than one option for programming. QMK is the common denominator and it isn't bad, but their are other options (Python, etc) and usually web-based configurators also.
...If you're willing to go with something that is too new to be popular, but has excellent ergonomics, programmable, and great customer support in US, I'd recommend Cyboard. [4] Currently waiting for mine to be shipped.
There are lots of options besides these. So you are correct split keyboards are not available at the local big-box store, but at the same time they are definitely more powerful, more comfortable, and more customizable as a class. They are out there and they have a following, just have to know how to get started.
[0] https://www.zsa.io/voyager/
1) not building it myself. I need off the shelf. I am lousy with a soldering iron.
2) it must have a dedicated F row. I do not care about layers and supposedly saved movement distance. I must always be able to mash F5 without any chording. Give me an F row + layers. The keys need to physically be there, my desk has plenty of “vertical” space to hold it.
Agree your requirements get into rarefied territory if you want something ready-to-go, split, programmable, with FN row. But there are options.
I am not affiliated in anyway, just a happy customer who is no longer in pain after work. Dedicated F row was a must for me as well.