MC 1.16.2
indrev-1.6.6-BETA
fabric 0.9.3+build.207
fabric-api-0.20.1+build.401-1.16
(Ubuntu 18.04.5 LTS, which shouldn't be relevant but sometimes is)

Instead of generating the expected biome-specific veins, the scanner is only returning veins of peat, lignite, and nikolite. This occurs even in vanilla biomes, including nether biomes (where by rights none of those veins should spawn).

I encountered the issue in AoF3-2.0.2, but replicated with just fabric-api, fabric-language-kotlin, and indrev installed.

Having had a poke through the code, I believe the biome check is failing somehow (since, if I've read it correctly, it defaults to minecraft:ocean, and that would match the veins I listed).

Thanks so much for this report, I had already found this issue and was about to rewrite the whole thing because I wasn't finding the main issue. With the 1.16.2 update, a lot of the way that biomes work have changed and I didn't notice that I had to change how I got the biome's information. I only noticed this after you mentioning it defaulting to Ocean. After this it was an easy fix and I'm able to find other veins normally now! The update may take a while to come out however because there are a lot of fixes/changes coming with them.