This is not a joke, but I don't think you could've even tried Ubuntu Studio as a professional - seems more likely you sniffed at it as a hobbyist and couldn't deal with it.
I haven't found it to be any hassle to get a working, stable and low latency setup with Ubuntu Studio AT ALL, but then I've chosen my hardware properly: Presonus for everything. Its amazing, and very good latency - exceeding even the results I get when I put a Mac on the same chain.
56+ channels of digital audio, countless external synths and effects, literally hundreds of onboard synths and fx and processing plugins, including some stuff that you won't get elsewhere. (Plus: sources for everything in case a professional engineer in our studio gets the urge to extend functionality between sessions...)
Yes, it works out of the box very well. Far less stress than getting a recent new UAD acquisition going on our iLok'ed Mac DAW, even.
(Catalina, FFS!)
>On Mac I install software and double click it. I plug in my interface.
All you do with Ubuntu Studio is install it and maybe do a package update using standard onboard tools. After this, the system is ready to go, out of the box, without too much fuss - all the apps you need to start recording multitrack professional audio - nothing extra to install, no iLok, and literally hundreds of amazing plugins, fx, synths, and so on to explore, already installed.
Ardour is easily a productive professional DAW, like any other, and REAPER is even native on Linux now, with a very easy single binary to download and double click .. matching your user needs on MacOS, even.
You should really give it a try if you haven't done so yet. Your prejudice for the mainstream might be keeping you from having an honestly astonishing experience.