In large organisations, you probably use teams to manage maintainer access to repositories. So here are a couple of scripts.
list-team-repos.sh will recursively enumerate all repositories visible to a particular team. Recurisive because teams might be nested and so child teams will grant access to further repos.
check-private-vuln-reporting.sh will list (and can be tweaked to set) private vulnerability reporting for a list of repos in the format emitted by list-team-repos.sh.
Both scripts use the gh CLI tool and you'll need to gh auth login first to run them.