Not sure what the hell is happening but during a roundcube upgrade :
Setting up ca-certificates-java (20161107~bpo8+1) ...
Error: missing `server' JVM at `/usr/lib/jvm/java-8-openjdk-armhf/jre/lib/arm/server/libjvm.so'.
Please install or use the JRE or JDK that contains these missing components.
Question answered on the forum. It was related to some packages badly installed before roundcube installation... hence it had nothing to do with roundcube :innocent:
Not sure what the hell is happening but during a roundcube upgrade :
c.f. : https://forum.yunohost.org/t/mise-a-jour-roundcube-impossible/4979 and https://arnauld.org/zerobin/?840cf8a8aa97dfb9#mOcYGGeCSsYT4gIFg1lse8Wm9Ok6vigPvsEhh4nAiyY=