Just don't make my mistake of using YouTube Music from your brand account on YouTube, or you'll always see this when trying to upload music:
Switch accounts to upload
You're signed in to an account that doesn't support uploading. To upload music, switch to your personal Google account. Learn more
There's no way to share or migrate liked songs, apparently. And YouTube Music never warns you about the upload limitation before you start using it from "the wrong account".
Please correct me if I'm wrong, but my understanding is that you can upload your music to YTM but it isn't seamlessly integrated into your listened experience like it is on GPM.
Is that right? If so, that is losing the best aspect of GPM.
The UI/UX of youtube music is lacking compared to GPM, but at least the file locker functionality that I use is still here.