Problem solved: Booting the Ubuntu system the timedate service didn't work (bug?). The date was one year behind. Therefore some certificates failed and thus some connections to repositories.
I changed timedate to ntp and all works fine! $ sudo timedatectl set-ntp no $ sudo apt install ntp $ ntpq -p $ date -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1920611 Title: ubuntu-20.04.2 for raspberry, java installation fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openjdk-11/+bug/1920611/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
