Ok, eiher I'm just too stupid, or the new SDK cannot be installed on my Efika with MorphOS 2.4 (and requires 2.5 to be installed first?).
When running the Installer program a window opens with a black picture and a red text "invalid data". That's already quite suspiscious, but maybe nothing serious?

The Install path will always append "Development" to it. Is that intended? But, no matter which path I choose, I even pre-created all directories, the Installer always tells me:

Installation failed:
filetype is unknown

What is wrong?