Hello, I recently tried downloading fabric loader to be able to use mods and shaders at the same time. I followed a youtube tutorial in order to do this. In the tutorial I had to download fabric loader, optifine, optifabric, modmenu, and fabric api. I also downloaded the Roughly Enough Items mod off of curse forge, just to test it out. After downloading these items, they showed up in my mod menu and REI was working. However, I ran into problems when trying to download and use different mods. I tried downloading the Better Biomes mod off of curse forge, and while I did download it and move it to my mods folder, It would not show up under my mods on minecraft. I thought that this was because it was not compatible with mizunos 16, however I removed mizunos 16 and it still wouldn't show up. Does anyone know a fix to this?
Forge & Fabric mods aren't compatible (unlike Forge & Liteloader back in 1.12.2), and as Biomes O' Plenty is a Forge mod it won't work (there is Fabric & Forge support methods like Patchwork but it's for 1.14.4 only at the moment but BOP is supported for it).
There is many biomes mods for Fabric though and Terrestria does similar enough for biomes in the overworld, while Cinderscapes would add the Nether biomes.
There is also some shaders like Canvas Renderer you could use, though I don't know enough about that side of Fabric mods/shaders so best to ask the Fabric team via their Discord or others in the community: https://discord.gg/v6v4pMv (#player support channel)