Sorry, I thought it was solvable through there! In any case, I managed to solve the issue this morning (JEI/REI conflict), so I will delete this post shortly.
Apparently I have duplicate mods installed in my custom profile, but I can't find out which ones they are! Could I get some assistance? I'll paste the debug log below (since I can't figure out how to physically attach it).
[10Feb2023 20:33:06.688] [main/ERROR] [net.minecraftforge.fml.loading.moddiscovery.ModDiscoverer/SCAN]: Failed to build unique mod list after mod discovery.
net.minecraftforge.fml.loading.EarlyLoadingException: Duplicate mods found
at net.minecraftforge.fml.loading.UniqueModListBuilder.buildUniqueList(UniqueModListBuilder.java:78) ~[fmlloader-1.19.2-43.2.0.jar%2395!/:1.0]
at net.minecraftforge.fml.loading.moddiscovery.ModDiscoverer.discoverMods(ModDiscoverer.java:105) ~[fmlloader-1.19.2-43.2.0.jar%2395!/:?]
at net.minecraftforge.fml.loading.FMLLoader.beginModScan(FMLLoader.java:166) ~[fmlloader-1.19.2-43.2.0.jar%2395!/:1.0]
at net.minecraftforge.fml.loading.FMLServiceProvider.beginScanning(FMLServiceProvider.java:86) ~[fmlloader-1.19.2-43.2.0.jar%2395!/:1.0]
at cpw.mods.modlauncher.TransformationServiceDecorator.runScan(TransformationServiceDecorator.java:112) ~[modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.TransformationServicesHandler.lambda$runScanningTransformationServices$8(TransformationServicesHandler.java:100) ~[modlauncher-10.0.8.jar%2382!/:?]
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) [?:?]
at java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1779) [?:?]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) [?:?]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) [?:?]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:575) [?:?]
at java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260) [?:?]
at java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:616) [?:?]
at java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:622) [?:?]
at java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:627) [?:?]
at cpw.mods.modlauncher.TransformationServicesHandler.runScanningTransformationServices(TransformationServicesHandler.java:102) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.TransformationServicesHandler.initializeTransformationServices(TransformationServicesHandler.java:55) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.Launcher.run(Launcher.java:87) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.Launcher.main(Launcher.java:77) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) [modlauncher-10.0.8.jar%2382!/:?]
at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:141) [bootstraplauncher-1.1.2.jar:?]
[10Feb2023 20:33:06.696] [main/ERROR] [net.minecraftforge.fml.loading.moddiscovery.ModDiscoverer/SCAN]: Mod Discovery failed. Skipping dependency discovery.
[10Feb2023 20:33:06.697] [main/DEBUG] [cpw.mods.modlauncher.TransformationServiceDecorator/MODLAUNCHER]: End scan trigger - transformation service fml
[10Feb2023 20:33:06.703] [main/DEBUG] [net.minecraftforge.fml.loading.LanguageLoadingProvider/CORE]: Found 0 language providers
[10Feb2023 20:33:06.707] [main/DEBUG] [net.minecraftforge.fml.loading.ModSorter/]: Configured system mods: [minecraft]