The entirety of the 26.3 Wilderness Bound update, backported to 1.21.1 and 1.20.1 for Neoforge, Fabric and Forge. 

Full feature list with future roadmap at the bottom:

The Dappled Forest:

• A new biome with orange grass, coarse dirt patches and a carpet of leaf litter
• Red, orange and yellow poplar trees, with shelf mushrooms growing on their trunks
• Fallen poplar logs covered in mushrooms
• Red shrubs, brown mushrooms, foxes and rabbits
• 17 types of Abandoned Camps across 16 biomes: tents and campsites with cushions, straw beds and loot, plus a map leading you to another camp

Poplar wood:

The full wood set: logs, wood, stripped variants, planks, stairs, slabs, fences, gates, doors, trapdoors, buttons, pressure plates, signs, hanging signs, boats and chest boats.

No Dappled Forest nearby? Every wandering trader sells poplar saplings for 1 emerald.

New blocks and items:

• Cushions in all 16 colors. Place one on any surface to sit.
• Straw beds: a cheap, single-use bed for a night in the wild. It won't move your spawn point
• Shelf mushrooms: bouncy, grow with bone meal, and work in mushroom stew
• Wool and concrete stairs and slabs in all 16 colors
• Leaf litter and red shrubs for decorating

Requirements:

• TerraBlender (automatically installed as a dependency)

Compatibility:

• Works alongside most biome mods that use TerraBlender (Biomes O' Plenty, Regions Unexplored and others)
• Mods that replace the whole overworld, like Terralith, stop the Dappled Forest from generating. Everything else still works

Future roadmap:

• Fabric support - Done! 
• Wilderness Bound: Dappled Creatures - custom companion mod for the biome, adding new creatures with cute behaviors
• Copper chests, lanterns and gear - Mostly ready to go, coming in v1.1
• More 2026 drops - whether here or through other mods, first up is baby mob redesigns from tiny takover, then I'll try at chaos cubed
• Idyllic forests - wildflowers, bushes and firefly bushes to name a few additions that will eventually be added

FAQ:

Can I use this on a server? Yes. Install it, and TerraBlender, on both the server and every client.

Fabric or other versions? Forge and Fabric supported for 1.20.1, Forge, Fabric and Neoforge support for 1.21.1.