Can I use an iMac mid-2011 as an external monitor with the 2020 Mac mini?
Can I use an iMac mid-2011 (21.5") as an external monitor (it has a Thunderbolt port) with the 2020 Mac mini?
Question marked as
While your 2011 iMac does actually support Target Display Mode.
Sadly all Mac's built after 2019 including the 2020 Mac Mini, do not support using an iMac as a display.
see > Use your iMac as a display with target display mode - Apple Support
"You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display"