How to set OpenCamera APP as Default Camera App

A long time ago I switched form stock camera app to “Open Camera App”, because the stock app didn’t work anymore with its settings to save photos to the memory card and support decided (as workaround) to do so. I’m very fine with the “Open Camera APP”. For usage with StreetComplete APP its now needed to set this APP as Default APP, but any hints there, how to do so, are not realizable, because of missing such menu points, options at all.

Any solutions?