I revived a late 2013 iMac that was collecting dust, and was disappointed to find that Target Display Mode no longer worked. So enter OpenCore Legacy Patcher, and now I'm now running MacOS Monterey with Universal Control and Airplay Receiver. Open source software is pretty great.
@den bookmarked this post for later, I want to check it out!
@m2m There's a video by someone called Mr. Macintosh who runs through the process nicely, and he apparently keeps it up to date. https://www.youtube.com/watch?v=go6RTCHv4GA
