aka org.kde.kscreen.osdService.showOutputIdentifiers and org.kde.kscreen.osdService.showOsd
kscreen has an osdmanager, where its osd are broken except since it seems 49c5d9c5 , except for the only important used one : the "select screen action" on screen connection.
AFAICT the other two: screen identification (the kcm has its own osd) and osdText are unused (https://lxr.kde.org/search?%21v=kf5-qt5&_filestring=&_string=kscreen.osdService)
The showText usecase is covered by plasma-workspace osd and identify output is implemented in the KCM.
So remove those to limit maintenance burden.