Apple Music app shows empty (no music in library) after every restart

I'm hoping for (but, to be honest, not really expecting) a quick/easy resolution to this issue, but considering I'm asking much the same question that went unanswered here, my hopes are minimal.

I use the Apple Music app only as a player for my local music library. I am not subscribed to the Apple Music service. All of my actual music files are located on my local drive. I don't let the Music app "manage" them, because I have my own preferred system of file organization, cover image management, etc. These files are necessarily located elsewhere other than the default location where the Music app wants them to be (or wants to copy them into), because they are regularly synced/backed-up to a non-Apple-based cloud service.

Why use the Apple Music app at all, then, you might ask? And that's a good question (getting better all the time, actually). I just like the interface (even though I still miss "cover flow").

But my appreciation for the interface is not enough to forgive the issue I've been experiencing, which is that every time I restart my computer and then open Apple Music, there's nothing in it. My song files and folder structure have not moved from their previous location on my local drive, they are just absent from the app, which presents an empty library. After every single reboot. Re-dragging/re-scanning all of it into Apple Music every time I restart is unfeasible/undesirable (especially considering the massive size of my local music library, we're talking close to 2TB here).

So what then can I do to get the app to not empty itself out anymore?