Ken, Drew, JMO, and everyone who responded: Thanks, and success! I have installed Photoshop Elements 2021 on my Mac (which solves the 64-bit issue) and VueScan which solves my Epson 4990 Photo scanner problem. In my case no change to connections, i.e. the scanner is connected to the Mac by USB and all is fine. VueScan interfaces directly with the Elements, i.e. when I do Elements/File/Import, I point it to the scanner, and it automatically calls up VueScan (where in my old version it would call up Epson Scan) and away I go.

I had some issues with the Photoshop Elements2021 install, but that was resolved and the VueScan download/install is a snap. So thanks again to everyone, and if anyone else is faced with a scanner that doesn't interface with Catalina or Big Sur, this is the solution. And Ken has a very nice write-up on using VueScan, the link is in his earlier post.