Use iMac 27" late 2014 as a display for MacBook Pro 2021 (M1 Max)
Does anyone know if I could use my iMac Late 2014 as a monitor/display for Macbook Pro late 2021? TIA
iMac 27″, macOS 11.6
You cannot.
Review the document: Use your iMac as a display with target display mode - Apple Support
Target display mode is a feature available with late 2009-Mid 2014 iMacs. The display Mac has to be running macOS High Sierra or older and the signal producing Mac has to be running macOS Catalina (ca. 2019) or earlier (your two Macs are too new to do this).