In that case, I’d recommend doing SSO with a live staging site.
Set up a second copy of discourse on the same-ish hosting, give everyone admin, and create SSO Provider Secrets for localhost:3000, localhost:4000, localhost:4001, *.cluster.local, etc as necessary.
Everyone on your development team will be able to forge authentication payloads from this site, so it’s important to document that and use your real production site for real authentication.