Books

BookWyrm is an open and federated alternative to goodreads. I use my instance's website and it's a decent experience. There's an Android app too but I haven't tried it.

Storygraph.

I've been using Openreads recently, it works pretty well. It's an open source app, all just on your phone, but it pulls info from open library. I also use storygraph lol, but I've been reconsidering it a bit because of the AI features

My favorite is hardcover.app as well, though I also maintain my data on storygraph. (I guess technically I maintain it on Goodreads too, but that’s only because calibre auto updates my reading)

I use Hardcover. Pretty good so far.

Though meant for another matter, as the name implies, Tuyware's "My Game Collection" (link) was pretty good for anything tracking from what I used of it some years ago. From my experience, it was good for its tagging system, the accompanying filters system, and the ability to add custom "platforms". Do mind, however, that some useful functions are paywalled, and they don't offer a single payment version, only a MTX-based payment to unlock those functions.

I just use Google sheets, I find the apps and websites all leave me wanting and more than once I've had em close so I leaving me needing to migrate by data or lose it.