Workaround for Dell's lack of drivers for macOS 10.15 Catalina?
The one-stop-shop for open source print drivers is here:

http://www.openprinting.org/printers

Models similar to your Dells seem to be supported. 

If the printers can interpret PostScript or PDF natively, then you should be able to get by with a 'Generic' print queue. This would not necessarily have device-specific controls, but should be enough to print.