Those problems were solved with manual sync through greenbone-feed-sync, I’m using the containers, which don’t have any script to synchronize as of Improved Feed Sync for Greenbone Community Containers . The images are updated daily, a simple pull and run should copy the updated feed to the volumes. Nothing wrong in the logs.
On that note, Workflows - Greenbone Community Documentation is outdated (I guess, since greenbone-feed-sync isn’t in the gvmd container).