Target Display Mode not working on MacBook Pro 13" 2020 I am using a 2011 iMac as an external monitor (and speakers) for my MacBook Pro (2014) on a daily basis. 

Last week, I upgraded to the 2020 MBP 13". The new MBPs with USB-C are supposed to work with Target Display Mode, using the Thunderbolt 2 to USB-C adapter. I have it connected with an official Apple Thunderbolt 2 cable and Thunderbolt 2 to USB-C adapter. But when I press Command-F2, nothing happens, like they aren't connected.

I can already rule out the cable/adapter/USB-C port being defective, because I've used for transferring files from the old MacBook to the new one successfully. It also still works fine when I connect the Thunderbolt cable (directly) to my old MBP.

Any ideas what I can do to debug the problem?

Edit: I tried it out with a colleague's MBP 2017, same cable and adapter, and it worked flawlessly. So the problem seems to be limited to the new 2020 MBP. I am in direct contact with a very helpful (and seemingly persistent) 2nd line Apple Support employee about this now, so fingers crossed.
Same issue here! 

New 2020 MBP, using an apple USB-C to thunderbolt adapter, apple thunderbolt cable, mid 2011 iMac. 

Apple support just informed me that they don't have this feature in newer devices. What a shame!

I'm filling out a feedback form suggesting that they bring it back. Perhaps naively hopeful that they'll respond but worth a shot.