I do use OSX, but I'm also on Linux Mint. Both are sharp and smooth as butter. I'm uncertain why your experience has been what it has with Linux. Could be drivers or something. I did have to set Mint to work for 4k60. It did not work out of the box properly. (HiDPI was off. Hardware vsync was off.) Mint has never had sub pixel rendering as far as I know. It looks crisp and great.
I think you misunderstand me. I am saying that on Linux text at normal PPI is pretty much as good (to me) as text at high PPI because it has sub pixel rendering and strong hinting that Mac OS X lacks,
OSX has had sub pixel rendering disabled by default since Mojave. It also never had the strong hinting that you can find on Linux and Windows which makes text significantly sharper at the cost of differing from the shape as specified by the font.
They were paying to license Microsoft’s ClearType patents and decided not to pay anymore once retina displays had become near standard for lost Macs and subpixel rendering was no longer necessary
If true, it's a pity they were paying. Apple's SPR goes back to the Woz days, whereas ClearType didn't come around until XP, and wasn't a default until Vista.
Also, apple has a tendency to support fancy features ONLY on its own hardware. I know apple retina displays allowed display scaling, but non-apple displays only let you set the absolute display resolution.
You generally have to use the right equipment -- using mini displayport or thunderbolt 3 instead of HDMI, depending on the generation. It's definitely finicky (much like getting guaranteed 4k60 output, especially through a dock)