Is it a bad idea to reach out to my manager’s boss about helping out on tasks?

There has been structural changes in my workplace lately that could open up job opportunities for me. I routinely talk to my manager about wanting to be more involved and I constantly offer to help with additional tasks that have a broader scope in the workplace. Their response is usually ‘thanks, I’ll keep that in mind!’ Or ‘yeah I could teach you about x, y, z!’ But then it goes nowhere. My boss’s boss was recently promoted and I told my boss that I’m happy to help with any tasks that come up while things are in transition. Would it be inappropriate to extend this same offer to my boss’s boss as well?