[nmerouze]

I don't see how you could work with a growth team on the side but if you are searching for a website with existing traffic maybe you could do marketing for a popular open-source project you like. It's not the ideal solution you described but it would allow you to learn marketing, even if it's by yourself. And you won't even have to make a product.

[wnbmt]

Wow, that's actually not a bad idea! Maybe I'll reach out to open source teams and hopefully help them get more downloads/traffic.

[CyberFonic]

This is an awesome suggestion!

So many open source projects would benefit from some good marketing.