I migrated using Migration Assistant from a late 2013 MacBook Pro to a MacBook Air with MacOS Big Sur 11.2.3. The MacBook Pro has iPhotos 9.6.1 on it with many photo in iPhotos. After the migration, the iPhoto icon is on the tool bar of the new computer, but clicking on it results in a statement that it is no longer supported. (Doesn't give me access to photos thru iPhoto.)
As recommended, I tried launching Photos with the option key held down. After doing this I thought I would see iPhoto library in the list of libraries, but I didn’t. Does this mean Migration Assistant didn’t migrate the photos? If yes, I wonder how to get them out of iPhotos on the old computer and into Photos on the new computer. (I still have the old computer with the photos in iPhoto.)
From Memory - in iPhoto >> There should be an Export function some place >> Export to and choose to Large External Drive. Then connect the drive to new machine and either drag and drop to Open Photos or again Import to Photos.
The iPhoto application is 32-bit and unsupported on Big Sur.
Look in your Pictures folder for the iPhoto Library. If it is present, launching Photos with the option key will produce a library selector that should offer the iPhoto Library as one of its options. The following from my macOS 11.2.3 on an M1 mini that was migrated from a Mojave Time Machine backup:
Okay. I'll give that a try. There's definitely no iPhotos library on the new computer. Guess it didn't migrate with Migration Assistant. Thanks for the suggestion. I backed my old computer up to a large external hard drive using time machine before migrating with Assistant. I'll have to check to see if the iPhotos are on the external hard drive. Maybe the missing library has something to do with using time machine. I don't remember now, not sure, but seems like the Assistant uses Time Machine somehow.