Exactly how does one get into a situation where your sound card isn't supported on macOS, other than by putting together a Hackintosh? :) You're going to have to look for some pretty edgy edge cases where you will be left rending your shirt and wailing "if only I could compile an open source driver for [insert thing] but the cursed closed nature of Apple products prevents me from doing so!" (I mean, I'm pretty sure people can write open source drivers on Macs if they want.)
Granted, as someone who's been using Linux sporadically in various ways for the same two decades I've been a Mac-on-the-desktop user, I can't remember the last time I was left rending my shirt and wailing "if only I didn't have to compile an open source driver for [insert thing] to get basic functionality working." (Although I can remember more than one time I ran desktop Linux in a VM on a Mac, and spent several hours doing web searches for how to get [insert thing] working to find little more than other posts saying "I'm running desktop linux on a VM on a Mac and I can't get [thing] working".)
Apple stops supporting their own hardware all the time. They dropped a bunch of video cards especially in recent releases of the OS.
How this translates is by Apple officially dropping support for your whole computer. I guess you consider getting trapped on an old OS that stops getting security updates and becomes incompatibility with the latest applications to be superior to the situation on Linux. I do not.
Or, as others have pointed out, having to upgrade perfectly good hardware because the OS no longer supports it. That has happened to me on both Mac and Windows.
Honestly, better hardware support is one of the reasons that I have started using Linux more and more than proprietary options.
I actually really like Windows 10 but I have had way more hardware issues with it on my primary laptop. I had odd performance problems with it sometimes and the mouse pointer would lock up frequently ( Windows factory installed ). I put Windows 11 on this computer ( new enough hardware to meet all the Windows 11 asks ) hoping it would improve things. It was a disaster. My Bluetooth headphones rarely worked. Plugging wired headphones into the port would not silence the speakers. Blue screen of death ( have not see that in years - looks much friendlier now ) all the time which you know is a driver problem. Anyway, I have since out Linux on it and all my hardware woes are in the past. As I said, I actually really like Windows but it is a relief to get it off this machine.
I've got an old Macbook Air that has to be used with a USB sound device because the internal hardware died at about 4 years but wasn't worth replacing the motherboard. In other cases, I'm sure professional (or even hobbyist) audio people use hardware other than the computer's built-in sound devices. How long do the makers of those keep updating the drivers when it's a 5 generation old product and their developers have moved on to newer projects? A driver they gave you for OS X 10.5 isn't going to do you any good today.
Granted, as someone who's been using Linux sporadically in various ways for the same two decades I've been a Mac-on-the-desktop user, I can't remember the last time I was left rending my shirt and wailing "if only I didn't have to compile an open source driver for [insert thing] to get basic functionality working." (Although I can remember more than one time I ran desktop Linux in a VM on a Mac, and spent several hours doing web searches for how to get [insert thing] working to find little more than other posts saying "I'm running desktop linux on a VM on a Mac and I can't get [thing] working".)