I recently bought a 16″ M1 MBP. My plan was to sell my iMac Pro and use the money to buy a nice display. Alas, selling such an expensive machine locally is not easy (I’m not willing to run a gauntlet of eBay fraudsters), so it looks like I will be stuck with it. I have Monterey 12.4 running on both machines, and with Universal Control I can now seamlessly use the same mouse & keyboard to control both. That’s fine, but there are occasions when it makes sense to extend my MBP’s display (connected to Pro Display XDR), for example when I am in Lightroom or Photoshop. This is doable using AirPlay, but Apple in it’s infinite wisdom (I’m being sarcastic) decided that when using an iMac as a secondary AirPlay display, the iMac’s resolution is limited to 3840×2160 (where all the interface elements are tiny) or to low res 2560×1440. Now before someone tells me that this is a limitation of AirPlay, consider that when used in a mirror mode over AirPlay the iMac is able to duplicate my main display in native 5K resolution just fine !!! Clearly there is no technical reason why this is not possible in extend mode. There must be some hidden software switch that Apple decided to turn off in order to nudge owners of old iMacs toward bying an Apple display (Studio or Pro XDR). Greedy ba$tard$! If anyone knows how to flip that switch, I and all others who are in my situation will be eternally grateful.
