DimensionalThreading VS lithium-fabric

The Dimensional Threading mod offers this on 1.16+ fabric servers

You don't need to redesign the server. You can just use these mods.

Dimthreads may cause some issues, though seemingly none that are similar to yours https://github.com/WearBlackAllDay/DimensionalThreading/issues. Also make sure you configured it to use more than 3 threads since you have additional dimension mods (Aether);

Starlight performs substantially better than phosphor and greatly speeds up terrain generation. Krypton for networking performance. C2ME or tic-tacs (both aim to do the same thing and are not mutually compatible) greatly improve world loading and terrain generation but are experimental and, in my experience, not compatible with a lot of other mods. Dimensional Threading puts each dimension on a separate thread, but also tends to not be very compatible with other mods. FerriteCore aims to reduce ram usage. This page has a whole list of mods.

(Experimental) Dimensional Threading ( WearBlackAllDay/DimensionalThreading )

SOLVED: Thanks for the suggestion! I just figured out the problem. I had the experimental mod called Dimensional Threading installed on the server https://github.com/WearBlackAllDay/DimensionalThreading.

Lithium: General performance boost. (not updated)

For Minecraft specifically, regardless of hardware and OS, you should be using Sodium and Lithium. These are third-party mods that fix a ton of performance issues - they make a huge impact especially on lower-spec'd machines.

i can confirm what mrspinn has posted but I would use rubidium and not magnesium(both ports of sodium, just a different authors on the ports.), this works with magnesium/rubidium extras as well for things like a better zoom function(runs off the sodium base so both ports are fine). Then if you'd like shaders with this you can use oculus(port of iris), this works with optifine shader packs. Road runner is good for cleaning up a lot of the overhead in things like game physics, AI, block ticking, etc (port of lithium, don't know why this one didn't keep the chemical name). Starlight again is good at what it does, even to the point of being integrated into papermc(which is why it's on their github and not the spottedleaf's personal anymore), don't know if you've sent much time around plugin servers. I also then use Ferritecore this greatly helps bring down memory requirements of the pack(I can run on 4gb, given I have fairly fast memory).

Lithium (further optimization, also by Sodium devs)

Sodium Phosphor Lithium also get iris but I don't have download link

Here’s a page on the config file if you want more info:github.com/CaffeineMC/lithium-fabric/wiki/Configuration-File

Are you using Optifine? That's the largest contributor to graphical issues. Instead, try Sodium and Lithium.

It's just that. It's a free and open source optimization mod that aims to improve fps, and fixes other issues. Along with that, Sodium is free and open source (available on GitHub). By default, Sodium does not provide shader support, and shader support can be done with Iris (Iris is also open source and free as well). But if you want to optimize your fps even more, you can bring in Lithium and Starlight (Lithium targets overall optimization, like the AI and other stuff without breaking the game, and Starlight is a complete rewrite of the vanilla lighting engine to be even more faster and fixes so much stuff with the lighting engine). And you can tack on more mods, like FerriteCore, Enchaned Block Entities (EBE) in order to optimize other parts of the game

Lithium v0.7.6