Very slow copy of very large photo library to new Mac-start over??

I just came home from work and in 10 hrs, it now says the library size on the Mac Studio is 210GB, and still moving. This is weird, I don't want to wait days and days for it to do whatever it is doing. Sad...

Part 1:

For Photos, I did have error messages and I ended up getting bumped up to a Senior Apple Support person. After getting error messages ("name or character too long for destination volume" which they sent a screenshot to Apple engineering to investigate) copying over the 452GB Photos library from an external SSD hard drive, I wiped the brand new Mac Studio hard drive and installed a fresh copy of Monterey (12.3.1). I made sure to turn off iCloud photos in my Apple ID login account (listed at the top of Systems Preferences) since I store everything locally only.

Then I tried again to copy the folder over to my account Pictures folder. I got a different error message that said it couldn't copy because a Photos library already existed (which it didn't because I had dragged it to the trash and emptied the trash). I found a post on the Apple discussion boards that said just drag the folder to the desktop to copy over and THEN drag it to the Pictures folder. That WORKED!!!

The Photo library transfer kept failing with the error message that the folder couldn't copy due to a "name too long or unrecognized character in the destination volume." I got bumped up to a Senior Apple tech specialist. He had me enter Terminal and type in some sync coding to copy the folder from the external SSD hard drive to the Pictures folder in my Mac Studio account.

I started it before I left for work and will see tonight if that worked. He said that usually works and if not the next step is to wipe the brand new Mac Studio hard drive and start over with a reinstall of Monterey.

At least the Photos folder is the very first thing I attempted to transfer (I did not use Migration Assistant so that I had a clean install from the old iMac with none of the crap)!

Part 2: From Mac Resources Forums

Steps from jsoto last yr (Jan. 16, 2021):

This worked perfectly for bringing my High Sierra iTunes library (that was on an external SSD hard drive) over to the new Mac Studio running Monterey-- and it worked to keep my Media and Purchases Apple ID tied to the Music app (separate from my different iCloud Apple ID). Just follow his steps-- THANK YOU jsoto 

And yes, also make sure that you Get Info (Command I) on the external hard drive and click ignore ownership on this volume. Thanks Fishrrman!

1. I de-authorized my M1 MBA on the Music App, then signed out of my account within the Music App.

2. Once that was done my iCloud Music Library was gone which is what I wanted.

3. I manually deleted the playlist names that iCloud Music Library left in the Music App.

4. Deleted the Music directory under ~user/myhomedirectory/music/music (it gets confusing because Apple Music App uses 3 directories with the same "Music" name.

5. Emptied my trash can

6. Copied my iTunes folder from my Mid 2010 MBP 15 i7 on macOS High Sierra to an external drive.

7. Then from the external drive copied the iTunes folder the the desktop of the M1 MBA

8. I option-started the Music App and selected to "Choose Library" option and pointed to the "iTunes Library.itl" file and it imported the playlists, artwork, etc. 

9. Then opened the Music App, followed by Preferences, under "Files" changed the music media location to the Music folder created from within the "Media" directory created by Apple Music App. 

10. Then proceeded to consolidate my library by having Apple Music copy iTunes Media over to the location I specified in the Music Preferences by using File/Library/Organize Library/Consolidate Files. It then copied all my iTunes Media over to it. 

11. Sign into the Apple Music App with my account.

12. Authorize my computer.

13. iCloud Music Library, iTunes Match, Apple Music subscriptions activated with my sign-in and computer authorization.

14. Zero issues with Apple Music App. Everything in working order.

15. Delete the copied iTunes Folder from my old MBP from the desktop of the M1.

16. Empty the trash.

17. Enjoy Apple Music App to learn the changes from iTunes.

Music and Photos are both working and have my 25+ years worth of content, albums, etc. So far everything is in working order!