Currently the mod is set to disable vanilla ores by default, making playing regular Minecraft near impossible.
This should be changed to true by default for ease of use or a notice should be placed on the mod's page.

Hey, thanks for pointing this out. I disagree with this being a good change for QOL, as it would defeat the purpose of the mod. When OSV disables world generation features, it replaces them with its own, and so coal ore and other vanilla-style ore veins still spawn out of the box.

I brought this up because vanilla veins like coal and iron don't spawn.
Perhaps this is a quirk of it running alongside Biomes O' Plenty?

Is this after any config changes at all?

I had a clean install of Biomes O' Plenty, Underground Biomes, and Ore Stone Variants.

The problem shouldn't be because of Underground Biomes, because UB fills the ore veins with standard Minecraft ores.

Ohhh that's what it is. There used to be an option in 1.12 to automatically ignore OSV ores if UBC was present, since that mod already adds them.

It is strange that no ores generate at all when both mods are installed, is it not?