As someone who has lived in 4 different cities and as many countries in the past 8 years, I would definitely use a "just moved to X city" service/app that helps

As someone who has lived in 4 different cities and as many countries in the past 8 years, I would definitely use a "just moved to X city" service/app that helps people who just moved somewhere make friends. It's a bit more narrow than what you are proposing but sometimes it's easier to start with a smaller niche and expand from there.