We have OpenSUSE Leap 15.4 x86_64 installed (inside a virtual machine).
We added the KDE3-Repository
(https://download.opensuse.org/repositories/KDE:/KDE3/15.4/) and installed
kde3-kommander and kde3-kommander-runtime to run a KDE3-kmdr-file as a wrapper
for a bash-script.
Installed is kde3-kommander-3.5.10-lp154.105.1.x86_64.
When starting only kmdr-editor or kmdr-executor, the KDE Plasma 5
Desktop freezes after seconds and only a reboot helps, killing processes
not.

The rare warnings when opening the programs in a console could help:
konsole: kmdr-editor
kbuildsycoca running
reusing existing ksycoca
libpng warning: iCCP: known incorrect sRGB profile
-> KDE Plasma 5 Desktop freezes

konsole: kmdr-executor ~/some_kmdr_file.kmdr
DCOPClient::AttachInternal. Attach failed. Could not open network socket
kbuildsycoca running
-> Sometimes it even opens, but it freezes after a few seconds. We also
tried to delete the users's cache (rm -rf ~/.cache), but this did not
help.

In Leap 15.4 in August 2022 kmdr-programs worked with the previous
kde3-kommander rpm package.

P.S.: In Leap 15.3 with kde3-kommander-3.5.10-lp153.105.1.x86_64 our
KDE3-kmdr-file opens and works fine.