My thoughts are related to what you call a Product. For example, consider LinkedIn. You would need several Product Owners for it, the key part is how you slice a giant system into several products. I could imagine the following:

- Feed

- Notifications

- Articles

- Posts

- Recommendations

- Jobs

- Network

And many others. I would see each initiative with a single Product Owner from end to end. Of course this is an example, and inside feed you would be able to slice even more but the point is: end to end responsibility.

In comparison to LeSS, I would see a CPO setting the context, and facilitating the collaboration among Product Owners; leading not managing. It's key to empower Product Owners to deliver outcome and make decisions without approval processes, and avoiding dependencies would be an important aspect to create value faster.

How does that sound for you?