Honestly, Windows users should be accomodated for as little as possible. I don't want to write my software once for 12 operating systems and once again for one. WSL is the only reason my software runs on their shitty OS at all.
However if you're goal is to have an impact with your software then supporting win32 is a good bet since you're going to find an order of magnitude more users on win32. You'll also probably want iOS, Android and other platforms that aren't drop-in ports for POSIX if you want to provide a reasonable interface.