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