In the generated smallrye-mutiny-vertx-core,  the io.vertx.mutiny.core.Vertx class has a reference to  io.netty.channel.EventLoopGroup:  

  public io.netty.channel.EventLoopGroup nettyEventLoopGroup() { 
    io.netty.channel.EventLoopGroup ret = delegate.nettyEventLoopGroup();
    return ret;
  }

But the module of io.smallrye.reactive.mutiny.vertx-core does not depend on module of io.netty.netty-transport where the EvengLoopGroup class is located.

So we need to update the module dependency.