How to import external libraries to my mod? (MC 1.17)

My goal is to connect DL4J library to a Minecraft mod, but there is a problem. I can't figure out to import the library correctly. I tried to modify the build.gradle file like this:

dependencies {
	minecraft 'net.minecraftforge:forge:1.17.1-37.0.21'

	implementation fg.deobf("org.deeplearning4j:deeplearning4j-core:1.0.0-M1.1")
	implementation fg.deobf("org.nd4j:nd4j-native-platform:1.0.0-M1.1")
	implementation fg.deobf("org.slf4j:slf4j-api:2.0.0-alpha2")
	implementation fg.deobf("org.slf4j:slf4j-simple:2.0.0-alpha2")
}

(where the dependency-block is positioned right before the jar-block at the end of the gradle file)

to import DL4J from the Maven repo but even though the script builds successfully, the libraries cannot be used in the Java code. I figured out that compileOnly and runtimeOnly solve the syntax errors in the Code but don't get imported by ForgeGradle (?) so that an NoClassDefFoundError is thrown when a method from the library is called (When JVM loads a class from the library).

What am I missing?