+1 to adding non-combat XP to the list please! There are some great interactions to be had with NPCs, and players should be rewarded for resolving non-combat situations.
From a personal perspective I'd also like to see this: I dunno how it fits in with D&D since, well, I don't really know anything about D&D (so I'm grateful to those who do!) but I've often thought that RPGs in general can be too combat-focussed for my tastes. XP from non-combat stuff goes some way to addressing that.
More catching up tomorrow. My brain needs a rest!
Many, many, many 5E campaigns eschew experience points for "milestone" leveling. Sometimes DMs award XP for non-combat stuff. it just depends on the DM and players. No good reason not to reward creative play, as others have suggested.