OUTPUT

I looked over other issues which involve adding the optifine jar mod into the mods folder, I did that but still got the same result. I'm afraid this might be a duplicate of an existing issue but so far I haven't seen one as relevant, let me know if that happens regardless.

"mods folder"

"the OptiFabric fabric.mod.json"

LOG:
Error encountered during mixin config postInit step'mixins.mm.json': Failed to setup optifine java.lang.RuntimeException: Failed to setup optifine at me.modmuss50.optifabric.mod.OptifabricSetup.run(OptifabricSetup.java:54) at java.base/java.util.ArrayList.forEach(ArrayList.java:1511) at com.chocohead.mm.Plugin.getMixins(Plugin.java:340) at org.spongepowered.asm.mixin.transformer.PluginHandle.getMixins(PluginHandle.java:128) at org.spongepowered.asm.mixin.transformer.MixinConfig.postInitialise(MixinConfig.java:667) at org.spongepowered.asm.mixin.transformer.MixinProcessor.prepareConfigs(MixinProcessor.java:542) at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:439) at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:415) at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:285) at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:208) at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:178) at org.spongepowered.asm.mixin.transformer.FabricMixinTransformerProxy.transformClassBytes(FabricMixinTransformerProxy.java:23) at net.fabricmc.loader.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:162) at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:154) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519) at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:466) at net.fabricmc.loader.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:50) at net.fabricmc.loader.EntrypointStorage$NewEntry.lambda$getOrCreate$0(EntrypointStorage.java:106) at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1224) at net.fabricmc.loader.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:104) at net.fabricmc.loader.EntrypointStorage.lambda$getEntrypointContainers$1(EntrypointStorage.java:191) at net.fabricmc.loader.entrypoint.EntrypointContainerImpl.getEntrypoint(EntrypointContainerImpl.java:37) at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:47) at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke(EntrypointUtils.java:33) at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:143) at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28) Caused by: java.lang.RuntimeException: An error occurred when trying to find the optifine jar: INCOMPATIBLE at me.modmuss50.optifabric.mod.OptifineVersion.findOptifineJar(OptifineVersion.java:44) at me.modmuss50.optifabric.mod.OptifineSetup.getRuntime(OptifineSetup.java:62) at me.modmuss50.optifabric.mod.OptifabricSetup.run(OptifabricSetup.java:41) ... 26 more

EDIT: I noticed that the message said it couldn't read the optifine version "1.16.x G8", which is confusing knowing that this mod is for 1.17.x

I would suggest redownloading the optifine jar file from here: https://www.optifine.net/downloads
Select the latest version even though they are all previews. Its quite strange that your optifine file is actually not a preview.

what do you mean? it's a "pre26" optifine in the folder, which is the most latest preview of OF at the time of uploading this issue.

This is the filename I get from downloading: preview_OptiFine_1.17.1_HD_U_G9_pre32.jar.
Dude just redownload.

Whoops, forgot to update. The issue is solved by installing the new latest optifine jar MOD which might happen the be doing the same, thank you for replying even though I don't entirely appreciate your pushy suggestion.