AdaptiveRuinedPortals

Ruined Portals have always had the same look. This mod changes the environment around the portal to the Nether biome it leads to, and the chest loot contains items specific to that biome! Such as Crimson Fungus and Roots around the portal that takes you to Crimson Forest, Bones and Wither Skulls around the portal that takes you to Soul Sand Valley, etc.

Nether Wastes

A small chance for Netherrack to turn into Nether Quartz Ore

Crimson Forest

Netherrack turns into Crimson Nylium
Crimson Nylium may sprout Crimson Fungus or Crimson Roots
Rare Shroomlights growing above the Nylium

Warped Forest

Netherrack turns into Warped Nylium
Warped Nylium may sprout Warped Fungus, Warped Roots, or Twisting Vines
Rare Shroomlights growing above the Nylium

Soul Sand Valley

Netherrack turns into Soul Sand, with a chance of Bone Block instead
Magma Blocks turn into Soul Soil
Soul Sand and Soul Soil may spontaneously ignite with Soul Fire

Basalt Deltas

Netherrack turns into Basalt
Magma Blocks turn into Blackstone, with a chance of Gilded Blackstone instead
A rare Wither Skeleton Skull may be found resting atop the blackened terrain

Little warning:
Vanilla Minecraft takes quite time to calculate position of the matching nether portal(if the terrain is hard for a portal to generate). Because of this, the mod can not 100% predict the portal's biome(especially if portal takes the player to the border of 2 biomes). I could write the code so it can predict, but then the mod would have to generate a few chunks, slowing down chunk generation on low end PCs.

Notice for Forge users:
Versions 1.0.0, 1.0.1, 1.1.0 works completely normal. But, the new portal's color change that is added on 1.2.0 doesn't work on .jar files, even though they work in dev mode. Sorry for Forge users.. :(
Also, Forge will be discontinued starting from 1.21.3