AlternativeTo is a site I use quite a bit. Personally I use it when I get fed up with an Android app having too many ads / creepy network behavior or want to find a self-hostable version of a freemium service.
It has filters for free, open source, platform type, etc. From my understanding it's all crowd sourced, so if you disagree with a rating put in a vote! Sharing this in hopes that others find it as useful as I do.
If you know of similar or better resources I would love to hear about them.
Edit: many people are noting that the comments and reviews are out of date. I agree! Despite that I still find it to he useful. It would be great if this little bit of visibility gets more folks engaged over there to improve it.
That's not really how the comments on alternativeto work. They are relative.
If you got to spotifys page, it will list similar services, each with their own comments, and the comments under youtube music, for example, will be about how it compares to spotify.
So, to leave useful comments, you only have to know how a given piece of software compares to what you used before. You don't comment on how a given thing compares to everything else, only to one thing at a time.
Then, as other people browse the alternatives, they can use those individual comparisons to navigate their way what they need. Stuff like "this can't replace that for this use-case, because reason, but it does this other stuff" is extremely useful when looking for something that does what you're looking for.