Just checked my oldest DELL Vostro PC still being used with the latest MS PC Health Check tool, and the hardware is not eligible for Windows 11. Specifically, the Intel Core i7 processor - a 2012 biz desktop. Will just keep using WIN10, though have gotten my money's worth in any case. System processors may end up being the limiting factor for eligibility for WIN11 upgrades.
My primary desktop a Dell Alienware 17" laptop w/TB Hub, and other notebooks are no older than a couple of years so should be eligible for WIN11. Though haven't run the hardware check on them yet.