THE 1.21.1 UPDATE

REMOVED:

[Let's Do] API
Aether Delight
Aether: Lost Content
Almanac Lib
Ars Artifice
Better Dogs X Doggy Talents Next
Botarium
Christmas Festivity
Colorwheel
Colorwheel Patcher
Distant Horizons
Embeddium Extra
Exotic Birds
Let Me Despawn
Let's Forge Bronze and Iron
Mobtimizations
Nvidium (Acedium)
Otyacraft Engine
Paintings++
Quark Delight
Serious Player Animations
Sodium/Embeddium Options API
Structure Gel API
The Aether: Redux
Trotting Wagons

ADDED:

AutoModpack
C2ME
Chunky
Climbable Ropes for Create Aeronautics
Create Aeronautics
Create Big Cannons
Create Propulsion: Simulated
Create Railways Navigator
Create: Automotives - Immersive Vehicles
Create: Copycats+
Create: Dragons Plus
Create: Neapolitan
Create: Power Loader
Cult of Azazel
DragonLib
Drippy Early Loading Module
Drippy Loading Screen
Effortless Building
Embers Re-Ignited
FancyMenu
Feature Recycler
Forge Config API Port
Framework
Fzzy Config
Get It Together, Drops!
Goety
Immersive Vehicles
Iris & Oculus Flywheel Compat
KubeJS
KubeJS Create
L2 Library
LambDynamicLights
[Let's Do] Farm & Charm
MCA Reborn
Modular Golems
No Chat Reports 
Ars Ocultas
Occult Engineering
Occultism
Occultism KubeJS
oωo (owo-lib)
Packet Fixer
Prickle
Rhino
Ritchie's Projectile Library
Sable
Sable Dynamic Lights
Screenshot Chat
SeeU
Separate Sable Render Distance
spark
Stellar View
Tuning Wrench
Voxy
Voxy Server Side

UPDATED / PORTED:

242 different mods (too long to post in a single patchnote) 

OTHER CHANGES AND FIXES:

ported the entire existing server world from 1.20.1 to 1.21.1

repaired over 7.2 million old blocks and registry IDs

restored thousands of missing or broken blocks, block entities, structures, inventories and saved mod data

repaired MineColonies positions, buildings, citizens, jobs, inventories, recipes and requests

repaired Create trains and preserved the existing railway data

cleaned up leftover data from removed mods including Aether Redux, Exotic Birds and VS Clockwork

added custom datapacks and KubeJS compatibility fixes for mods that changed IDs or recipes during the port

pregenerated chunks in all dimensions, including a 1000 chunk radius square in the overworld

added AutoModpack so the server can automatically keep everybody's mods synced and updated