The mod Breaks my server by not letting anyone join.
Any help is appreaciated.

I have found these possibly important lines:

[09:56:12] [main/FATAL] [ne.mi.fm.lo.RuntimeDistCleaner/DISTXFORM]: Attempted to load class net/minecraft/client/entity/player/ClientPlayerEntity for invalid dist DEDICATED_SERVER
[09:56:12] [main/WARN] [mixin/]: Error loading class: net/minecraft/client/entity/player/ClientPlayerEntity (java.lang.RuntimeException: Attempted to load class net/minecraft/client/entity/player/ClientPlayerEntity for invalid dist DEDICATED_SERVER)
[09:56:12] [main/WARN] [mixin/]: @mixin target net.minecraft.client.entity.player.ClientPlayerEntity was not found ars_nouveau.mixins.json:ClientElytraMixin

So maybe it has something to do with Elytras?

Here are my logs:
`
[10:19:06] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher running: args [--gameDir, ., --launchTarget, fmlserver, --fml.forgeVersion, 36.2.8, --fml.mcpVersion, 20210115.111550, --fml.mcVersion, 1.16.5, --fml.forgeGroup, net.minecraftforge, -nogui]
[10:19:06] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher 8.0.9+86+master.3cf110c starting: java version 1.8.0_292 by Oracle Corporation
[10:19:07] [main/INFO] [ne.mi.fm.lo.FixSSL/CORE]: Added Lets Encrypt root certificates as additional trust
[10:19:07] [main/INFO] [mixin/]: SpongePowered MIXIN Subsystem Version=0.8.4 Source=file:/home/maximilian/Dokumente/kok/libraries/org/spongepowered/mixin/0.8.4/mixin-0.8.4.jar Service=ModLauncher Env=SERVER
[10:19:07] [main/INFO] [mixin/]: Successfully loaded Mixin Connector [vazkii.patchouli.common.MixinConnector]
[10:19:07] [main/INFO] [cp.mo.mo.LaunchServiceHandler/MODLAUNCHER]: Launching target 'fmlserver' with arguments [--gameDir, ., -nogui]
[10:19:08] [main/FATAL] [ne.mi.fm.lo.RuntimeDistCleaner/DISTXFORM]: Attempted to load class net/minecraft/client/entity/player/ClientPlayerEntity for invalid dist DEDICATED_SERVER
[10:19:08] [main/WARN] [mixin/]: Error loading class: net/minecraft/client/entity/player/ClientPlayerEntity (java.lang.RuntimeException: Attempted to load class net/minecraft/client/entity/player/ClientPlayerEntity for invalid dist DEDICATED_SERVER)
[10:19:08] [main/WARN] [mixin/]: @mixin target net.minecraft.client.entity.player.ClientPlayerEntity was not found ars_nouveau.mixins.json:ClientElytraMixin
[10:19:12] [modloading-worker-2/INFO] [ne.mi.co.ForgeMod/FORGEMOD]: Forge mod loading, version 36.2.8, for MC 1.16.5 with MCP 20210115.111550
[10:19:12] [modloading-worker-2/INFO] [ne.mi.co.MinecraftForge/FORGE]: MinecraftForge v36.2.8 Initialized
[10:19:13] [main/INFO] [patchouli/]: Loaded book jsons on Thread[main,5,main] in 18 ms
[10:19:13] [main/INFO] [STDOUT/]: [com.hollingsworth.arsnouveau.client.particle.ModParticles:registerParticles:23]: Rendering particles
[10:19:13] [modloading-worker-1/INFO] [STDOUT/]: [com.hollingsworth.arsnouveau.common.capability.ManaCapability:register:62]: Finished Registering ManaCapability
[10:19:13] [modloading-worker-1/INFO] [STDOUT/]: [com.hollingsworth.arsnouveau.api.familiar.FamiliarCap:register:97]: Finished Registering FamiliarCap
[10:19:13] [modloading-worker-1/INFO] [STDOUT/]: [com.hollingsworth.arsnouveau.common.network.Networking:registerMessages:27]: Registering packets!!
[10:19:13] [Forge Version Check/INFO] [ne.mi.fm.VersionChecker/]: [forge] Starting version check at https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json
[10:19:14] [Forge Version Check/INFO] [ne.mi.fm.VersionChecker/]: [forge] Found status: OUTDATED Current: 36.2.8 Target: 36.2.19
[10:19:15] [main/INFO] [mojang/YggdrasilAuthenticationService]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api.mojang.com', sessionHost='https://sessionserver.mojang.com', servicesHost='https://api.minecraftservices.com', name='PROD'
[10:19:15] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, destination] and [teleport, targets] with inputs: [Player, 0123, @e, dd12be42-52a9-4a91-a8a1-11c01849e498]
[10:19:15] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, location] and [teleport, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
[10:19:15] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, location] and [teleport, targets] with inputs: [0.1 -0.5 .9, 0 0 0]
[10:19:15] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, targets] and [teleport, destination] with inputs: [Player, 0123, dd12be42-52a9-4a91-a8a1-11c01849e498]
[10:19:15] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, targets, location] and [teleport, targets, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
[10:19:15] [main/INFO] [minecraft/SimpleReloadableResourceManager]: Reloading ResourceManager: Default, forge-1.16.5-36.2.8-universal.jar, curios-forge-1.16.5-4.0.5.3.jar, Patchouli-1.16.4-53.2.jar, geckolib-forge-1.16.5-3.0.46.jar, ars_nouveau-1.16.5-1.22.3.jar
[10:19:16] [Worker-Main-13/INFO] [minecraft/RecipeManager]: Loaded 10 recipes
[10:19:17] [Worker-Main-13/INFO] [minecraft/AdvancementList]: Loaded 927 advancements
[10:19:18] [Server thread/INFO] [minecraft/DedicatedServer]: Starting minecraft server version 1.16.5
[10:19:18] [Server thread/INFO] [minecraft/DedicatedServer]: Loading properties
[10:19:18] [Server thread/INFO] [minecraft/DedicatedServer]: Default game type: SURVIVAL
[10:19:18] [Server thread/INFO] [minecraft/MinecraftServer]: Generating keypair
[10:19:18] [Server thread/INFO] [minecraft/DedicatedServer]: Starting Minecraft server on *:25565
[10:19:18] [Server thread/INFO] [minecraft/NetworkSystem]: Using epoll channel type
[10:19:18] [Server thread/INFO] [minecraft/DedicatedServer]: Preparing level "world"
[10:19:18] [Server thread/INFO] [minecraft/MinecraftServer]: Preparing start region for dimension minecraft:overworld
[10:19:20] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
[10:19:20] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
[10:19:20] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
[10:19:20] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
[10:19:22] [Worker-Main-12/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:22] [Worker-Main-8/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:22] [Worker-Main-12/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:22] [Worker-Main-8/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:22] [Worker-Main-8/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:23] [Worker-Main-13/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:23] [Worker-Main-9/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:24] [Worker-Main-8/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 83%
[10:19:24] [Worker-Main-12/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 86%
[10:19:25] [Worker-Main-14/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 89%
[10:19:25] [Worker-Main-10/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 91%
[10:19:26] [Netty Epoll Server IO #1/INFO] [ne.mi.fm.se.ServerLifecycleHooks/SERVERHOOKS]: Disconnecting Player (server is still starting): Server is still starting! Please wait before reconnecting.
[10:19:26] [Netty Epoll Server IO #2/INFO] [ne.mi.fm.se.ServerLifecycleHooks/SERVERHOOKS]: Disconnecting Player (server is still starting): Server is still starting! Please wait before reconnecting.
[10:19:26] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 97%
[10:19:26] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Time elapsed: 7655 ms
[10:19:26] [Server thread/INFO] [minecraft/DedicatedServer]: Done (7.809s)! For help, type "help"

[10:19:37] [Server thread/INFO] [minecraft/MinecraftServer]: Stopping server
[10:19:37] [Server thread/INFO] [minecraft/MinecraftServer]: Saving players
[10:19:37] [Server thread/INFO] [minecraft/MinecraftServer]: Saving worlds
[10:19:37] [Server thread/INFO] [minecraft/MinecraftServer]: Saving chunks for level 'ServerLevel[world]'/minecraft:overworld
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (world): All chunks are saved
[10:19:43] [Server thread/INFO] [minecraft/MinecraftServer]: Saving chunks for level 'ServerLevel[world]'/minecraft:the_nether
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM-1): All chunks are saved
[10:19:43] [Server thread/INFO] [minecraft/MinecraftServer]: Saving chunks for level 'ServerLevel[world]'/minecraft:the_end
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM1): All chunks are saved
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (world): All chunks are saved
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM-1): All chunks are saved
[10:19:43] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM1): All chunks are saved

`

Are you running a native forge server, and are you running Vivecraft?

Native Forge. I eventualy got it working by hosting a LAN-game on port 25565 (by using "/publish 25565", if anyone is wondering), but that still isn't really a good solution