I do it via GitHub CLI:
gh label clone <source> --repo <target> --force
- cli.github.com/manual/gh_label_clone
- napjose.ph/posts/copy-issue-labels-from-another-github-repository
- stackoverflow.com/a/77946467
Example
gh label clone ginoi-com/site --repo keyclampstore-com/m --force
✓ Cloned 61 labels from ginoi-com/site to keyclampstore-com/m