It is not possible to open a different Library with AppleScript. It always open the last opened library.
tell application "Photos"
open "/home/benutzer/Pictures/Testlibrary.photoslibrary"
activate
end tell
Works for me, but check your path - I’m guessing home was supposed to be Users.
Thank you. You are right, ist was my fault. But after the correction I became a different failure.
The Photos - App was opened with the library it was opened bevorFollowing Error: The Programm "(null)" has no rights to open "Testlibrary.photoslibrary".