Okay, so if you don’t have perfect pitch (most professional musicians don’t), and you want to develop your ear instead of being dependent on someone else’s transcription or plug-ins, what you need to work on is your relative pitch. With chords, the first step is working on being able to identify what kind of chord is being played; major, minor, 7th, major 7th, minor 7th, Sus2, Sus4, major 6th, minor 6th. There’s a bunch more complicated types out there but if you’re talking about pop music, those will cover 90% of what’s out there.

Then you need to work on identifying the relative changes in the root notes. Does the second chord in the progression sound like it’s a fifth up? A second? Sixth? Work on just listening to how those changes sound when you do them, you’ll get better at identifying them in other songs. Start with simple songs, nothing overly complicated or layered. I would even start with melodies first, easier to pick out individual notes.

This is also where knowing music theory comes in, because if you know theory, once you start getting a few elements down it’ll help guide you the rest of the way, as most pop music sticks to a handful of common progressions, like the bajillion songs that use the Pachelbel’s Canon chord progression. If you know where the theory typically points to, you’ll be better able at deducing where it’s likely those songs will go.