The 2E DMG resists setting one XP system. Most of the text suggests DMs improvise awards based on how players foster fun, improve, and reach story goals—and by the way DMs can award XP for beating monsters. The loose approach parallels 5E and that surprised me.

How did your 2E campaigns handle XP?

@dmdavid 1/2 We played 2e and certain things were givens, e.g. defeating an opponent…. But the bulk was GM fiat for good character decisions and role -playing. Several of us rotated through GMing but once when I was a player I remember being awarded a nice little bit of XP when my cleric used a protection from weather spell and some real world avalanche survival training to, well, survive an avalanche. My GM ruled that the weather spell (basically an arcane umbrella)…
@dmdavid 2/2 …prevented the snow from packing so tightly around my character that he couldn’t move. Then my character used the drooling spit trick to determine which way was up (gravity pulls spit down) so my character could dig out and rescue some of the others. Got a nice bit of XP for that whole little scene.
@dmdavid So long ago. I believe I learned the lesson of "award XP for objectives and play" from Star Frontiers, long before 2E and incorporated into my Basic and Advanced D&D games.
@dmdavid Thinking on it some more. David "Zeb" Cook and Steve Winter did work on Star Frontiers together, and they worked on 2E together, so maybe it is a precursor to the idea.

@dmdavid I seem to recall that for our AD&D 2e campaign I gave out XP for monsters, but with a percentage bonus (5% to 15%) for ideas/role playing.

We did play with the class specific rules at one point. I remember the 2xp per gp for rogues seeming excessive, so we limited it only for gold gained whilst actually thieving.

That was 30 years ago though, so my memory is hazy.

@dmdavid If memory serves I tried using the individual awards system described in the DMG, saw it was completely broken in actual play and switched back to the BECMI system.
@dmdavid I did monster XP plus XP based on class and race roleplay