lithium VS Indium

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

I did find this on the issue tracker (https://github.com/comp500/Indium/issues/207) Which version of Fabric API are you using? 0.84.0 or newer is required.

Iris Shaders + Sodium - Link - Indium - Link - (Indium is needed for many other Sodium based FPS increasing mods) - Increases performance and shaders performance

Fabric has its own optimization mods. For performance, there is a great Sodium mod. To optimize the Lithium game world. To optimize Phosphor light. These are the main Minecraft optimization mods for Fabric. For shaders there is an Iris mod. Also, if you're playing with Fabric mods, don't forget the Indium rendering mod.

Indium (Required for Sodium compatibility)

You'll need CIT Resewn (and possibly Indium, but I'm not 100% sure). After this, you can follow any tutorial on how to make such resourcepack for OptiFine or MCPatcher, as CIT Resewn supports both.

indium github.com/comp500/Indium and continuity www.curseforge.com/minecraft/mc-mods/continuity allow you to have connected textures with sodium and lithium

If you don't also want Forge mods, they list the combination of Continuity and CIT Resewn as alternatives. (While not directly related to this usecase, if you go that route I would recommend also installing Sodium, Indium, Lithium, and Starlight.)

Indium to make Sodium compatible with some of the following mods.

Since they were Linux computers, then I assume they play Minecraft Java, which means there's a lot of ways to optimize the game to make it run a lot faster, sometimes even 3 times faster. This tutorial fully explains how to download Fabric mods, and this modpack is the best way to optimize Minecraft. The modpack might be a little complicated to download but it's absolutely worth. I downloaded just 2 mods (Sodium and Indium) on a computer that turns into a slideshow when Chrome is opened but they made Minecraft playable. The modpack also allows for shaders that make Minecraft look much better, almost like AAA games with RTX on.