Introduction:
I've made this datapack so me and my dude could try ourselves out in a more hostile and harder environment. Since Nether update beta when we tested the nether wastes single biome mode we wanted to beat the game this way, starting in the nether. This datapack pretty much makes our dream come true since I added river and plains biomes too so you can sill basically complete the game with villagers, water, animals around and I even modified ores so they'll spawn in every biome, including nether ones too and regardless of height.

Features:

Nether Wastes, Soul Sand Valley, Warped Forest, Crimson Forest, River (for water), Plains (for villagers and wool) biomes generate
Villages, pillager outposts, mines, strongholds, nether portals generate in random places
Ores generate regardless of altitude
Water does NOT evaporate from anywhere
Piglins and Hoglins do NOT turn into zombies
Custom sky, water, grass and foliage colors

There are two variants available for download. Normal which includes a load of ghasts being present in nether wastes and soul sand valleys which in my opinion increase the difficulty which is cool and one that removes ghasts from the overworld.

I've made a resource pack specially for this type of world that adds 1 hours and 16 minutes of dark, other-worldy ambient music to the game replacing the default peaceful ones.

Check out my other works too!

The End Overworld

Ocean Only / Water World

Everything / Every biome in one world!

[World Generator] Floating Nether Islands