currently the source build guide is in an intermediate state. The installed greenbone-feed-sync version doesn’t fit to the used gvmd version anymore. That’s due some chicken and egg issues and finding some problems with the docs while updating the source build guide to the latest components. Hopefully that will be fixed today.
Until the guide is updated, please run greenbone-feed-sync with the --feed-release 22.04 argument when using gvmd < 25.0.0 because the latest release of greenbone-feed-sync 25.1.0 will use a different feed version with an adjusted directory layout not fitting to your gvmd version. I added a disclaimer to the README of greenbone-feed-sync now.
I updated my last comment in regards of the CLI argument to use for an old feed release. The 25.1.0 release of greenbone-feed-sync renamed the --feed-version argument to --feed-release. The term feed version was used ambiguous and I hope the change improves the situation. Sorry for the inconvenience.