I found the answer in the forum openHABian hassle-free openHAB Setup
how to install the “zulu cryptography extension kit” which solved the problem
wget http://cdn.azul.com/zcek/bin/ZuluJCEPolicies.zip
unzip ZuluJCEPolicies.zip
cd ZuluJCEPolicies
cp *.jar /usr/lib/jvm/zulu-embedded-8-armhf/jre/lib/security
reboot
Many thanks to @Oggerschummer “Pälzer Bu” who posted the solution there.
(by the way: I’m a “Pälzer Bu” also but now living in Tirol / Austria where the mountains are a bit higher than the hills “in de Palz” 
)