Adding/syncing external Media folder to Apple Music on new Mac

Hello team,

Due to its large size, I have always stored my Apple Music media library (ie. Media folder) on an external HD. It contains a mix of songs and albums purchased through the iTunes Store as well as numerous items ripped from my own CD collection. My problem is getting my new iMac to recognize the local copies in that external Media folder. Although I have gone in to Settings | Files | Change... and pointed Apple Music to that external Media folder, it basically just created a new empty "Music" folder inside of it...but is not seeing the thousands of songs and albums already there.

My entire music library is also in the cloud thanks to iTunes Match, but I'm trying to get the local copies of all of it recognized by the Apple Music app on my new Mac mini. Unfortunately when selecting Get Info on any song, it lists the location as "Cloud" instead of showing the path to the local copy. I tried copying over the Music Library.musiclibrary from my old iMac, but that still didn't seem to help. I tried using the Consolidate Files option under File | Library | Organize Library, but that also didn't seem to do anything.

So...what are my options here? I feel like when I ran into a similar issue years ago and dropped all those external items into the Automatically Add to Music folder, I wound up with duplicates of everything – and when we're talking a music library containing 4,282 albums and 40,780 items total, I don't want to have to sort through that number of duplicates yet again. There has to be a way to point Apple Music to that existing Media folder on the external HD and just get it to "see" everything there without having to re-import it all. What am I missing?

Thanks very much in advance for any suggestions.