Music playlists deleted after attempting to restore library

My Playlists have all disappeared, and following all the steps in online support threads is just making it worse.

This started when I bought a new iPhone 17, loaded my Library, and all the album covers were mixed up. I followed online advice to delete the library and app on the phone (the phone was NOT plugged into the computer when I did this), reload Music, and then sync the library again -- and this time, all the album covers were correct, all the albums and artists are there.

But all my playlists were duplicated and appeared by their titles in the sidebar, but all but five of the most recent ones were empty. Twenty-five years of playlists (almost all made up of my own ripped CDs). Online advice said to move the library to my desktop and then import a recent version of the library. That gave me a spinning wheel for a day, and then all of my Playlists were deleted -- the names aren't even in the sidebar any more.

I don't have a Music subscription. I don't do algorithms. I make my own playlists from CDs. This all worked quite well since the dawn of iTunes until two days ago. Grateful for any assistance.