As there is no armhf version of the install.sh script for Virtualmin and installing it on a RPi3 I used this instruction:
It looks outdated but it works.
Now I noticed I do not receive any updates to virtuamin. There is no distribution source for armhf debian jessie. So that explains.
Of course I like to stay tuned with new versions.
Can I manually upgrade virtualmin by just installing the latest version over current version without losing configurations and data?