I don't think most users could cite what changed between Windows versions. 7->8->10->11.... it's been such a wash. But Linux users see a lot of little things they expected, now semi available.
Microsoft is definitely stealing from the best, and the best ideas are clearly originating on Linux & in open-source.
I cant find any evidence of a predecessor to Synergy on Mac. Synergy was launched in May 2001, initially for for X11.
Good ideas always happen elsewhere. GUIs getting ripped off of of Xerox is no surprise. Overall there is, I'd claim, extremely little genuine innovation in UIs. GNOME seems to be one of the few out there willing to keep re-beginning, doing radical refreshes, but it's still not like boldly vastly different than other things. But Linux users, with their libre attitudes, are out there exploring & finding what is possible & what makes sense, across dozens of window mamagers & thousands of add-on components & endless exploring/reconfiguring... not just consuming. Of course MS is watching & borrowing the emerging stuff.