Undo "Import from MacOS Photos library"

I inadvertently imported files from my Big Sur Photos library via the Import “Aperture/Photos” dialog.

Is there a way to stop that from synching? I already get photos automatically imported from my devices with cameras.

Yes, you can delete the folder in Mylio that those photos come into. It should be under Apple Photos/device name library. Deleting the folder will break the sync connection to that device.

If you want to retain the photos in that folder you’ll need to move them elsewhere first. It is likely, however, that the photos there are duplicates since you’re already importing them form your other devices (iphone/ipad).