As I remember it, Skylake machines were pretty thin on the ground in 2015 due to early issues; 2016 or 2017 would be a more reasonable origin date. Most SKUs didn't even launch til 2016, and Kaby Lake desktop processors only seem to have shown up in mid-2017.
It works on anything with a Haswell or later and Intel or AMD graphics, essentially.
(Note that the MacBook is 2015 because there was no product called that between about 2009 and 2015; the iMac Pro is 2017 because that's when it was introduced).
Yeah, Apple obsoletes a product 7 years from when they last offered it. The 2014 models of Macbook Air/Pro go obsolete this year and won't get the next macOS. The 2015 models will go obsolete next year, 2023. Windows 10 will still be supported on the grandparent's skylake vintage 2015 PC until 2025 when Apple will be obsoleting the 2018 Mac hardware.
Windows 11 works too, the workaround is official and at the same time windows 10 still receives updates so it's not like Microsoft killed older hardware by setting new requirements for Windows 11.
Sure, but the issue is uptake of Windows 11. Virtually no-one is going to use a workaround, official or not, so the low uptake is unsurprising, due to poor hardware support.