Here’s a solution Homematic HmIP-BROLL & HmIP-FROLL - Get them to work in openHAB which worked great for my 9 HmIP-BROLLs with OH / Alexa.
Problem for me was not so much that the above didn’t work, I just lacked some context / “how-go-guideline/quickstart”, which @Bredmich was able to provide exceptionally.