I know the app in the appstore does not support ios 7 and under. But would it be possible to get somehow an ipa of a version that is supported by ios 6.1.3?
No. The reason is that the tools that create the binary won’t allow it - as far as I can tell. But I don’t have an old iOS device. Not sure there are even sim files for iOS 6.1.
You could try to compile it yourself and side-load it. Apple made the entire dev process very complicated and many things aren’t just possible anymore.
But maybe there’s someonw on this forum who can help.