Setting up Support Slack locally

Slack is SaaS-only, so "local" means a throwaway Slack workspace + app whose OAuth and events reach your laptop. The job has one non-obvious idea that avoids almost every wall: the OAuth connect and the event webhook have opposite reachability needs, so you point them at different places.

• OAuth connect is browser-mediated. Your browser follows the redirect, so localhost is reachable. No tunnel needed.
• Inbound events (Slack POSTing messages so they become tickets) are server-to-server from Slack's cloud. Slack cannot reach localhost, so this one needs a public tunnel.

Keep the whole app and the OAuth flow on localhost, and point only Event Subscriptions (and Interactivity) at the tunnel. This also sidesteps free-tier tunnel rate limits, since the tunnel then carries only Slack's low-volume event POSTs rather than the entire SPA.