What is the best site/app to keep track of games across multiple libraries?

I’m pretty new to PC gaming, but my library across multiple platforms and launchers is starting to grow and it’s starting to get harder to keep track of what I already own where.

I have games on Xbox, Steam, GoG, and Epic.

What is the best website or app I can use to help me start keeping track of all my games? I would like to be able to access it on both my computer and phone if possible. Thank you for any suggestions.