Running 2E now, and there are other methods. This is from the revised book but the 1989 edition had similar listing in XP (these aren't nearly as good as killing things for XP but they were other ways you could gain XP). It has a lot of optional approaches in the system.
There were individual XP awards. You get rewards for RP, for participation, for clever ideas, etc:
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Then they had class based awards (you basically get rewarded for doing what your class does):
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This is the chart for defeating foes by HD. One important thing to note here is you can't get XP for killing something without 'significant risk' to themselves. The GM has room to interpret what this means but the book says a 7th level character in need of one XP can't round up his friends and surround a single orc, expecting to get XP. And you don't have to kill the creature to get the XP, you just have to defeat it. The values below get much greater if a creature has good abilities. A mountain Loup Garou has 7 HD but is worth 4,000 in the Ravenloft monster section of the ROT boxed set.
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They can also gain XP for things like story goals. So while you can't get XP for driving out orcs from a village without facing them at significant risk to the party, you can get story XP for that, you can get XP for the clever idea that caused them to be driven out, etc. And you can also grant XP simply for survival. These amounts are largely left up to the GM (thought it says in an earlier section story XP should not exceed XP for combat from an adventure):
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And you can still get XP for gold (on top of the thief's individual XP for gold):
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I should say I haven't been making heavy use of this (I've just been leveling the party at regular intervals because I am running them through an anthology adventure (and they need to be the right level to play each scenario). But reviewing this section, it matches my memory that much of 2E is about options and giving the group leeway to take different approaches. My guess is moving in this direction was a way to meet criticisms from players who felt you should get more XP for things you physically defeated, but still allow for other approaches to be important.
Not saying this is the best system, or that it shouldn't be XP for gold (think that call is somewhat subjective). But it is a little more involved than just getting XP for killing things