openvas-docker I had the same problem and this following page:https://sys-guard.com/post-18431/ helps me to resolve the Problem. It's in Japanese but you can translate into English. Like explained in the link, the prblem is from the files usr/sbin/greenbone-nvt-sync | greenbone-certdata-sync | greenbone-scapdata-sync. The link: feed.openvas.org is not available since 30 September 2020. The link will help you to change it into the new link.😊