How to make outlines around 2d objects?

Well, one possibility I can think of now is that you create a duplicate of your sprite, make it a child of your original sprite, color the duplicate sprite black or whatever you want the outline color to be, and then scale it just a tiny amount bigger than your original sprite and position it correctly under your original sprite. You should now get a somewhat decent outline effect. Here is an image to show you what I mean.

I also remember that in this Brackeys video he made an outline glow effect using URP and shader graph. I guess you could use this but if you don't want the glow effect you could just make the colors intensity 0 so it doesn't glow.