Changing Music Library - An unknown error occurred (--42076)

I'm assuming this is a fairly common predicament due to the sizes and costs of new Mac internal SSDs. I have an aging Mac with 1 TB internal drive, and I'm replacing it with with a new Mac that has 500 GB internal storage. The only item that's too big to fit on the 500 GB is the iTunes library - about 870 GB. I don't subscribe to Apple's Music.app. I copied the Data volume of the older computer (which appears to be working, just slow) to an empty 1 TB SSD using Carbon Copy Cloner 6, then (working with the old system still) used the instructions at https://support.apple.com/en-us/HT210230 to select the library from deep inside the user folder on the external drive. The items appear in the Music main window, but I received an error message: "An unknown error occurred (--42076).", and playing the items doesn't seem to work in Music.app. Carbon Copy Cloner is the only way I've found to copy the library to the external drive without error, because when I use Finder, the process stops before completion with various errors. The old Mac has been upgraded as far as possible, so I'm using Catalina.

Is the answer to wait until the new computer contains all the migrated data except the internal Library folder (I would have to delete that before migrating to accommodate the smaller drive, right?)? In other words, is Monterey less likely to produce that error?

Am I instead going to have to re-add the media files to TV.app again once I have successfully selected an empty library on the external drive?