How do I find dependencies causing class duplication?

You need to exclude the arch Jar. First of all check where the duplicate comes from. You can see it if you print your dependency tree with a gradle task:

./gradlew -q dependencies app:dependencies --configuration compile

Then exclude the older arch Jar like you did for glide but with the correct exclude, for example:

implementation ('android.arch.persistence.room:runtime:1.0.0-alpha1') {
    exclude group: "android.arch.core"
}