Aristois

Do not install it from the marketplace, you need version 4.0.4 which is not the one there.

You need to download it from Modrinth and place it in .minecraft/libraries/me/deftware/EMC-F-v2/latest-1.21.4/

Remove all texture packs, including programmer art

There is no such file with this name. It is EMC.jar

https://discuss.aristois.net/topic/515/questions-regarding-donation

You can update the Fabric loader version in the json file in the version folder.

I don't think the java server thing is related to Aristois. I am able to run the mod with 21. You can try changing it in the installation settings though.

We are no longer accepting donations. You can read here: https://discuss.aristois.net/topic/515/questions-regarding-donation

It's probably due to Iris then. Have you tried without these mods?

Unfortunately I don't know what the cause of this issue is

Disable all texture packs including programmer art (in vanilla game)

It happens sometimes with some shaders. You can try playing around with shader settings or different shaders.

Can you send a screenshot of it? Are you using Iris or optifine shaders?

Change your graphics to fast or fancy

Good to know.

Search the entire prism folder for EMC.jar to see where it ended up. You can manually move it to the mods folder

The latest forge version we support is 1.20.1, so it wouldn’t even be possible to install to forge on 1.21.1

No. This is not possible

Are you sure you selected the forge box? This looks like a fabric install. For forge it will ask which instance to install to

Remove all texture packs including programmer art (through vanilla game)

It is due to a mod conflict so it's hard to tell

No, the new version has large render changes that require fixing. There is no ETA on 1.21.5 and I would not expect to see it in the near future if at all