Catalina on 2013 iMac no longer does Target Display Mode

[Jobeo]

My 27" 2013 iMac no longer is available in TDM to my 2016 rMBP. This was still working when my iMac was running Mojave. The rMBP is running Mojave still, and this worked before I upgraded last night...

Seeing some posts but did not find anything official. Most posts are people asking to bring TDM back to newer iMacs (if they did I would buy a newer one).

Can't understand Apple. A second iMac as a display to another make perfect sense, either that or sell plain iMacs as displays because who wants an ugly LG/Dell next to a beautify iMac/iMac Pro?

 

[Roxy.music]

I had the same issue and managed to go back to Mojave after a long process because i had deleted my
Mojave backups. I had earlier downloaded Mojave and tried to get it back on here but it said i could not.
So i had to go through a long process.I am glad i got it back on here.