I did use migration assistant for my new iMac 2020, transferring from iMac mid 2011. So Migration seems to have worked, but Photos and iTunes library did not come accross.

Possibly, but first get you photo library moved over. Once you do, restart the computer in Safe Mode and then restart normally and test.

The Photos app does not migrate, all that migrates is the library (or it's supposed to).

You did not explain how you migrated but below is the correct method, why is it correct....simple because it works 100% of the time.

When you buy a new Mac the easiest, quickest and most reliable method is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts. 

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps) , data files, settings, it does not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not a big deal. 

Your welcome, if you feel this issue has been solve, please mark the thread as such, it may help another user.

We have no idea where your photos were located on the Mid 2011, if they were in the Photos app then they were migrate into the Photos app on the new Mac. What I'm trying to say, is we need you to be more specific in your post.

Again, we don't know where your iTunes library was stored, if it was on the internal drive it's now in the Music App, so please look there. If you stored the iTunes library on an external drive then you have to pint the Music app to that location.

Does your new Mac have the same amount or more storage as the old Mac, if it does not that may account for the problem.

• If that is the case then on the old Mac open the Photos app and look in it's preferences to see where the library is located.
• Then navigate to that location and copy the library to a flash drive.
• Next copy the library from the Flash drive to the new location.
• Finally to open the library, double click it and Photos should launch and open the library and at the same time learn where the library is now located.