Mate 20.04 found my printer which was great but allocated a Cups driverless driver. I knew from past experience that this would not work so I went into Properties and clicked to "Change...". This started to load the "Search for driver" form and then just locked up. 3 times tested with same result. I then installed the correct driver and created a new printer and disabled the default printer that was originally found.
I solved my problem but the lock up does not happen in other desktops,