Hello,
and welcome to this community forums.
The Greenbone Community Edition supports CVSS3.0 since version 21.04 like announced here:
- GVM 21.04 (end-of-life, initial release 2021-04-16)
- Announcement: Full CVSSv3.0/v3.1 Coverage in feeds
Keep in mind that various vulnerability tests (VTs) might not have a CVSSv3.x score assigned (yet) for various reasons.