The openandromaps forum brought up the idea, that if mapsforge libraries are NOT supported, also Tiramisu should not work. So may be it is only PARTLY supported and Elevate2 could work. So it does!
As I fear the beta-version could corrupt my system-setup if installed together with the normal version, I decided to better wait for the next final version.
This is just to keep you and others updated.
Thanks a lot!