This Data Pack can help you build a nether world.
Dimensions:
  Overworld:
    It would generate like the nether.
    Sun and Moon run as usual ,though they're invisible.
    You can find stronghold here.
    Zombie villagers spawn in nether wastes biome.
    Witches spawn in crimson forest biome.
    Pillagers spawn in soul sand valley.
    Wandering traders spawn in the overworld.
    Respawn anchor works.
  Nether:
    Much alike the nether before 1.16,but neither mobs nor structures can spawn here.
    Just a hub.
    Respawn anchor works.
  End:
    The end mainland consists of netherrack .End stones can be found on the small islands.
    Chorus plants are removed ,but the flowers can be found in the chests of end cities.
    You can find snowballs in the end cities.
    Respawn anchor does NOT work.
Usage:
  Unpack the data pack;
  Move "nether_data" folder to somewhere you can touch easily ,like Desktop.
  When you generate a world:
    Open the "nether_data" folder and run randgen.bat or seedgen.bat;
    Open seed.txt and copy the seed in it;
    Go back to Minecraft;
    Click "Data Packs";
    Drag and drop the "nether_data" folder into the Minecraft window;
    Click yes;
    Click the triangle on the stone picture to move "nether_data" to the right ,even if the version is wrong;
    Click "Done";
    Click "More World Options...";
    Paste the seed;
    Now you can change things like game mode;
    Create new world.
    If there are warnings ,click "Proceed".