After spending a couple hours dealing with this same issue last night (and I didn't elect to do the update, Apple FORCED it on me because they want everyone using Apple Music), I found this solution: 12.2.0 disaster
-Quit iTunes
--Start iTunes while holding down the Option(Alt) key.
--A window comes up with an option for "Choose Library". Click that.
--Navigate to your iTunes folder, which should be in the Music folder on your hard drive
--Find the folder that says "Previous iTunes Libraries"
--Click the .itl file dated today, or the very most recent one you can find before you updated, and click on it.
Problem for me is that my last itl file was in December, so everything I have done to iTunes in the last 6 months was lost. I had to redownload all of my purchases, go find all my non-iTunes mp3's from the last 6 months, and my playlists and updates to song details (year, composer, etc) all have to be redone. This is DAYS worth of work that I have to do all because Apple couldn't keep their pants on about this stupid Apple Music service. So let's recap:
1) Apple forced an update on me
2) It caused me to lose 6 months of iTunes work
3) I called them, spent 15 minutes waiting to speak to someone about this, explained the situation, he put me on hold twice, then came back on with a "senior level tech" who promptly hung up on me (accidentally or not, who know) and no one attempted to call me back (even though I gave my number up front)
4) Apple makes good products (most of the time), but the company is horrible.