Summary

MultiYggdrasil is a Forge | Fabric | NeoForge server-side only mod, this means some functions may have bugs when running LAN server on client, for example, MC-52974.
It allows the server to set multiple Yggdrasil API sources, including the official and other external authentication servers.
Config design is inspired by MultiLogin, Some codes are borrowed from authlib-injector under the AGPL-3.0 license.
patchwork

Deploy

Java requirement follows Minecraft versions, no need to install authlib-injector, no pre mods, and no need to add or modify JVM arguments.

Same as the most part of other mods, there are only three steps:

1. Download mod
2. Throw it into mods
3. Launch the server

Configuration

A template:

# This config is located at config/multi-yggdrasil.toml
[SomeRandomMirror]                       # The name, can be set freely, has no impacts.
type = "OFFICIAL"                        # The type, now has 2 types, "OFFICIAL" and "BLESSING_SKIN".
sessionHost = "https://a.random.mirror"  # The specific value of "OFFICIAL" type. The tail of URL *should not* has '/'.
ordinal = 0                              # The ordinal, decided the order of use for this source

[MojangOfficialAPI]
type = "OFFICIAL"                        # When using "OFFICIAL" type, there can be no sessionHost property,
ordinal = 1                              # and it will use the official API.

[LittleSkin]
type = "BLESSING_SKIN"                   # ↙ The specific value of "BLESSING_SKIN" type. The tail of URL *should* has '/'.
apiRoot = "https://littleskin.cn/api/yggdrasil/"  
ordinal = 2