what DVD software works on my imac external superdrive

my apple USB superdrive is working just fine with the built in DVD player. like you, i too have a 2019 27" iMac that is currently running 12.3.1. first i need to ask, is the superdrive connected directly to the mac? or through a hub? besides that, there's a couple of things you can try.

first, go to System Preferences > CDs & DVDs and check and see if the options of what happens when you insert a disk have reset themselves.

if not, then you can shut down the mac, disconnect the superdrive, power the mac up, then reconnect the superdrive and test again.

if that didn't work, i would then try and reset the NVRAM / PRAM as well as reset the SMC.

Reset NVRAM or PRAM on your Mac - Apple Support

How to reset the SMC of your Mac - Apple Support

What do you mean it does not work? What exactly happens when you try?

Note that in recent versions you won't find DVD Player in /Applications, as before; but it is still there.

You can however search for it with Spotlight and then keep the icon in the Dock, for example, or make an alias and put that wherever you like.

FWIW, it is now located in /System/Library/CoreServices/Applications

i'm glad to hear that you've got it working.