I recently started using OpenVAS/GVM and wanted to know if OpenVAS v20.8.1 is equivalent to GVM 11? Looking at the FAQ, I see that OpenVAS was renamed to GVM, but on the GitHub page it is still named OpenVAS.
Maybe you should read the FAQ again. All your questions have been answered already there.
Greenbone started to lead the development, added several software components and turned OpenVAS into a vulnerability management solution still keeping the values of free software.
after the release of the OpenVAS 9 framework it got renamed to Greenbone Vulnerability Management (GVM) and released as Greenbone Source Edition (GSE). Since GVM 10 the term OpenVAS is only used for the scanner component as it was at the beginning of the project
Especially Which release contains which component
You should definitely stop using GVM 11 and switch to GVM 21.04 (or at least, 20.08). GVM 11 has many bugs and issues especially when using multiple scanners. GVM 20.08 onward is much more stable and resilient.
That’s not related to the original question but yes GVM 11 (and also all versions below) is obsolete and unmaintained. You should upgrade to the latest release.