I assume the nVidia experience is not recent? They’ve ramped up Linux efforts significantly. Even if despite officially embracing nouveau they’re still a bit toxic, in practice it should be expected to work fine (though see below, and apparently there were some issues with 5.9 specifically).
As for Kickstarter projects with proprietary drivers targeting only Windows and/or OS X, well, yeah...
You’re right that with proprietary closed-sourced drivers one has to be prepared to be a bit cautious or conservative when upgrading the kernel. Though unlike Windows there’s no real reason to always be on the most recent version (critical kernel security issues are rare).
Running a 4.x kernel is still considered bueno.