Apple documentation infers late 2015 iMacs (or Macs) can download and run Ventura. So why is this not showing on my software update as available? If it's because Apple wants me to buy a new iMac; even that is fine; but there is no new 27" or 32" iMac, at least not yet.
Not sure where you saw that but only 2017 and later iMacs can install Ventura. See the following: macOS Ventura is compatible with these computers - Apple Support
Not sure where you saw that but only 2017 and later iMacs can install Ventura. See the following: macOS Ventura is compatible with these computers - Apple Support
Only 2017 and later iMacs can run and install ventura
Upgrade to Ventura on late 2015 iMac
