New version of Photos (sw: Bilder)?
On start of Photos on my iMac (running macOS Catalina - 10.15.7) I get a message saying: "Not supported library... This library is from a newer version of Photos. Upgrade appl to be able to open library."
Previous use of the library was on my new MacBook Air running macOS Big Sur (11.3.1 - Apple M1).
Is this what causes the problem?
iMac 21.5″, macOS 10.15