WD - My Passport for MAC 1TB External Drive compatible with Catalina OS?

As long as you are using macOS to manage the drive then yes the WD drive is compatible. If you are using the WD software, then you need to contact WD to see if their software is compatible as I'm sure the WD website may contain misleading information.

FYI, it is much safer to just have macOS manage the WD drive. To do so just move everything on the WD drive to another drive temporarily. Then use the WD software to disable any security features on the WD drive. Then uninstall the WD software by following the manufacturer's instructions. Now use Disk Utility to erase the WD drive as GUID partition and MacOS Extended (Journaled) if you are only using it on a Mac or as GUID partition and ExFAT if you will share it with a Windows computer. Now move all your files back to the WD drive.

Once everything is working you can upgrade to Catalina. Just make sure to have good verified working bootable backups before upgrading in case something goes wrong or you decide you don't like Catalina and want to revert back to the current macOS.

Same question. Ever since I upgraded the OS system (iMAC) to Catalina, My Passport for MAC 1TB External drive stopped backing up through Time Machine. Keeping "failed" message.