Where do you find people for collaborating?

I was wondering where you can find people for collaborating on an app, because I recently started programming one and realized it’s too much work for me to do alone. It’s an (offline) app about keeping track of transactions between individuals and groups. Yes, apps like this already exist. My goal is not to earn money, but to learn something and have fun.

I’m a beginner/intermediate ionic programmer and think one or two extra people is enough.

Is anyone interested? Do you know where I could find people who might want to join? I thought about using gitlab for code-sharing, do you have any other recommendations for tools or workflows when collaborating?

Thanks in advance