Are hackathons outside of Facebook (i.e. MLHackathons) considered a COI? If so, is it just for Eng team or everyone?
Nope. creating something outside of Facebook is not a COI. Well unless you make a shitty social site that has no privacy 😉
Family, girlfriend, hobbies, or sleep are all considered conflicts of interest with FB. Remove these distractions or get PIPd
Creating a better product in your spare time, which isn't saying much.
Why would a hackathon be considered conflict of interest?
Creating a product outside of work.
Then no dev can do hackathons