For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rhabacker:branches:windows:mingw:win32:snapshots/openSUSE_Leap_15.6/home:rhabacker:branches:windows:mingw:win32:snapshots.repo
zypper refresh
zypper install mingw32-umbrello5-portable
For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rhabacker:branches:windows:mingw:win32:snapshots/openSUSE_Leap_15.5/home:rhabacker:branches:windows:mingw:win32:snapshots.repo
zypper refresh
zypper install mingw32-umbrello5-portable