Helping a tour guide friend with local SEO

A friend is asking for help with local SEO & optimising their GBP. I've helped local businesses targeting local audiences a ton but with my friend's audience, it'll be from people in other locations and countries. I tried doing the opposite and looking for tour guides in other cities and can see the local packs still show up albeit without the call buttons immediately showing. I see that I can still optimise their GBP in a lot of the same ways I would a usual local business but should I target key international cities as service areas? Anything else I should be aware of for this type of use case?