You can make it anonymous by creating an account with a different username that you don't use anywhere else and a burner e-mail via SimpleLogin or AnonAddy or 10minutemail. Maybe also a VPN? And in the case of StreetComplete, uploading changesets manually at random times.
There's no way to not make a public trail, that's just how mapping works, but you can make it really hard to trace back to you. You also have to understand that no surveillance capitalism is at play here, there's no actor that will consume this data and use it to feed you ads or content.