Using GTceu 1.20.1-1.4.0 and JEI 1.20.1-15.18.0.79, any recipe types added by GT do not show up in JEI. Crafting table recipes added by GT do appear. This seems to be the issue:
[18:15:17] [Render thread/ERROR]: Caught an error from mod plugin: class com.gregtechceu.gtceu.integration.jei.GTJEIPlugin gtceu:jei_plugin
java.lang.NoClassDefFoundError: com/gregtechceu/gtceu/integration/ae2/util/SerializableManagedGridNode
at java.lang.Class.getDeclaredFields0(Native Method) ~[?:?]
at java.lang.Class.privateGetDeclaredFields(Class.java:3297) ~[?:?]
at java.lang.Class.getDeclaredFields(Class.java:2371) ~[?:?]
...
Caused by: java.lang.ClassNotFoundException: com.gregtechceu.gtceu.integration.ae2.util.SerializableManagedGridNode
at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:525) ~[?:?]
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:137) ~[securejarhandler-2.1.10.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:525) ~[?:?]
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:137) ~[securejarhandler-2.1.10.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:525) ~[?:?]
... 87 more
Worth noting I guess that this is a heavily modified version of the community pack which I manually updated to GT 1.4.0