I learn by ear.
First I figure out the key.
There are only 12 so if needed I just play the barre chord shape of the F and go up the neck.
After I have the key I determine the chord 'shape' the song is played in.
For instance the C shape sounds different from the D shape, which sounds different from the G shape.
After knowing the key, the shape tells me whether I need a capo to play that shape in that key.
Next, the chords.
Fortunately many songs are just I, IV and V, with one of their relative minors thrown in.
When it's more complicated I can sometimes 'feel' the chord; if not ...
Is the mystery chord major or minor?
Is it a standard triad of only 1 3 and 5, or is there 7th or 9th thrown in?
Listen, experiment, try chords.
Eventually you'll find it and the more you do this ear thing the better you get at it.
Obvious complicated music, like jazz, takes much more time and work to become proficient at figuring out by ear.
Rarely will I need to look up a chord.
Often when I do the morons on Youtube or those who write 'tabs' or chords show the wrong chord ...... even sources with high view counts.
Ear training is fast becoming a thing of the past.
I blame the Internet.