Version: 5.0.8+1.19.2
Didn’t see any mention of this in future patch notes

Somewhat difficult to reproduce -

1. Locate a Buried Treasure Map with the chest coordinates inside a Volcanic Island (the tricky part)
2. Dig at the exact coordinates according to the map NBT.
3. No chest generates.

Let me know if this is too vague to reproduce or solve and I can try to get a seed/location.

Oooh, thank you for the report. At a guess, that structure probably won't replace volcanic rock. Maybe if I'm lucky there's a tag for it. I'll take a look. (I've noticed they quite amusingly screw with shipwrecks and ruined portals, too ... structure y placement is very hard-coded since 1.18.2, annoyingly.)

Ouch. Very hard-coded. I think I'd have to mixin with a complete reimplementation of the structure generator to fix it. They look for a hard-coded list of stone types and they replace with hard-coded stone/sand types too. Also they trust the value from Heightmap.Type.OCEAN_FLOOR_WG and only look down from there, which is a separate issue I need to address at some point. Structures seem to decide their placement before our code (and some of Mojang's own code) updates that.

OK, for a bit I wasn't sure why we even have buried treasure, because we don't use that structure tag. But here's vanilla's definition of the structure tag:

{
  "replace": false,
  "values": [
    "#minecraft:is_beach"
  ]
}

So indeed we've got buried treasure. Volcanic Island is in BiomeTags.IS_BEACH.

I'm going to look into this but I'm not yet certain what direction I'll go with it. If I am going to override vanilla's structure gen for this, I'm going to do it with a slightly modified structure custom for our biome. ;)