Interval training will help https://www.musictheory.net/exercises/ear-interval

Each interval has a unique "flavor" and once you can hear them you should be able to hear multiple intervals at the same time, which effectively identifies the chord. (Admittedly for complex jazz chords it can get very difficult and you probably need more powerful tools, I can't say.)

Well, the guitar has a finite number of strings and each string is partition into a finite number of frets. It's definitely not more than, say, 30^6 ~ 729 million.

That said, common chords are A, B, C, D, E, F, G (and their sharps and flats), combined with either major or minor mode. Hence "C, G, F, Am, Em" is an example of what someone could play. Now, of course, if it doesn't sound exactly like a G, perhaps it's a G7? After some practice, you can even hear, by the sound of the strings, exactly which chord it is. Em, G, and D are particularly simple to recognize.

Theory will make it a million times easier. Figure out the key and changes and you'll have likely chords and if you can do substitutions you'll have some alternatives.

Even if they're not exactly what was played, you'll be able to get to a working version with the right idea.

In any case, theory and experience will narrow the field down a great deal so you're not just stabbing at things in the dark.

It wouldn't hurt to know how to do the 'cowboy chords' and then the 'barre chords' before (or in parallel to) doing the transcriptions. Anyway, you should start with easy songs that mostly just include those until that seems easy.

> infinite number of combinations you have to try before you find the correct one?

Kinda, but on Guitar, most pop songs are major/minor, possible sevenths. I think this post is aimed at someone who can read tab, but isn't "good" (what ever that means) so they should have an understanding of basic chord shapes.

The post does imply that this only really works if you can comfortably read tab, which is probably 6month-2 years of work (part time)

You don't have to get it right. If you know the basic guitar chords in the open positions, you can sort of play along to the vast majority of popular songs. As your hearing, knowledge of the neck, and maybe music theory improves you will start to recognise more things.

The point is not a perfect outcome. The point is the effort.

In some genres there are an infinite number. Most of the music regular people listen to is diatonic though and uses either power chords or triads, and then there are not that many options.