I have an iMac retina 5K 27 inch late 2014 with iMacOS Big Sur 11.7.10 - Is there any way to use this iMac as a Display for a Mac Mini 2023

Sacly no, due to the newer MacOS & device...

The following older iMac models can be used as an external display when plugged into another older Mac model.

iMac models introduced in 2011, 2012, 2013, and mid 2014

To use any of these iMac models as an external display:

• The iMac used as a display must have macOS High Sierra or earlier installed.
• The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.
• The cable connecting the two Mac computers must be a Thunderbolt  or Thunderbolt 2  cable.

24-inch and 27-inch iMac models introduced in 2009 and 2010

To use any of these iMac models as an external display:

• The iMac used as a display must have macOS High Sierra or earlier installed.
• The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed.
• The cable connecting the two Mac computers must be a Mini DisplayPort  cable.

Use your iMac as a display with target display mode - Apple Support