For openSUSE Leap 15.4 gcc12 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rhabacker:branches:windows:mingw:win64:kmymoney5-kf576/openSUSE_Leap_15.4_gcc12/home:rhabacker:branches:windows:mingw:win64:kmymoney5-kf576.repo
zypper refresh
zypper install mingw64-kmymoney5
For openSUSE Leap 15.4 gcc10 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rhabacker:branches:windows:mingw:win64:kmymoney5-kf576/openSUSE_Leap_15.4_gcc10/home:rhabacker:branches:windows:mingw:win64:kmymoney5-kf576.repo
zypper refresh
zypper install mingw64-kmymoney5