You should be able to still add the printer on macOS using the built-in “Generic Postscript PPD”.
If Xerox driver features are really needed, you could try an unsupported work-around in which you install the Xerox macOS Common Print Driver from a closely related product like the Xerox® WorkCentre 6515 Color Multifunction Printer, which is supported on Catalina. Note: that there may be incompatibilities that could cause not all features/functions to work properly
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