Ever the optimist, I upgraded my iMac to macOS 11, Big Sur.

I should have waited, as I normally do, for the rest of the world to catch up.

Oops: Epson doesn't yet provide printer drivers for all printers and scanners, including my 3880 printer. Installing a 10.X version didn't work for me.

According to Epson's macOS Big Sur 11 Support "Epson will provide macOS Big Sur 11 drivers and software for Epson products on an on-going basis.": in other words, hopefully sooner than later.

On the other hand, a macOS 11 driver for EPSON Scan 2 software is already available.