iPhone 6s to iPhone 15 data transfer

We weren't able to transfer the data at the apple store because the 6s was full (64GB) and needed and IOS upgrade from 12.3 to the latest -- which user didn't want to upgrade. So, we were told that we could backup to the temporary icloud storage available for transferring data to new phone - however, still needed to update IOS - didn't do that. So next I have tried backing up to MacBook pro with Catalina and backup was successful. Was able to start restoring to the new iPhone 15 through iTunes. It's been over an hour and it still syncing. My question: Given that it's transferring about 55 GB of data to the new phone (256GB), could it take hours? There is really no way to tell if it's stuck (no progress bar). iTunes says it's 'Updating iPhone' and phone screen says 'Restore in Progress'. This is the second attempt. First attempt same situation but I decided to unplug the iPhone 15 from the Mac and it said it was partially restored (this was about an hour). Thoughts?