How about this.

Author: K1rakishou

Kuroba/app/proguard.cfg

@@ -120,4 +120,4 @@
 # Proguard keeps removing files that are used by the native library so it causes crashes.
 # This seems to fix the issue.
 -keep class com.github.k1rakishou.chan.core.lib.** { *; }
--dontwarn java.lang.invoke.StringConcatFactory
+-keep class java.lang.invoke.StringConcatFactory.** { *; }