So I noticed this issue a few months ago, I didn't think about it when I tried adding Astral Sorcery structures to Fronos, only for them to not load, but now I'm noticing this is an issue with using the JustEnoughIDs or the RoughlyEnoughIDs mod. For some reason, instead of using Biome ID 86 (for Fronos River), the mod will load in a different Biome entirely. And it's even more apparent when using the Biomes O' Plenty mod.

The biome info for the "Fronos River" sections are taken through the TellMe mod. If this is more an issue on JEID/REID's side, I'll have it reported over there, too.

Mod versions used to test this with:
More-Planets-1.12.2-2.3.3-GC4.0.6
BiomesOPlenty-1.12.2-7.0.1.2445-universal
JustEnoughIDs-1.0.3-57
RoughlyEnoughIDs-2.0.8
tellme-1.12.2-0.7.0-dev.20200919.184303

No JEID or REID/No BoP

REID/No BoP

REID/BoP

JEID/No BoP

JEID/No BoP

Closed with this fix on REID's side
TerraFirmaCraft-The-Final-Frontier/RoughlyEnoughIDs#42 (comment)