1. Log into Github, go to your account settings and click Register a New Application.
2. Fill in the application name (it can be anything, though your users will see it during the sign in flow). In Homepage URL, put your account’s authorization domain, found in the authorization domain section of the Cloudflare Access dashboard. It is likely https://something.cloudflareauth.com. In Authorization callback URL, put your authorization domain followed by /cdn-cgi/auth/callback. Click Register Application.
3. Copy your OAuth ID and secret and paste them in the Cloudflare dashboard to finish connecting Github.
Do you see a 404 page and does the URL contain:
No worries, this is super quick to fix. Here is what you need to do.
Go back to your account settings: https://github.com/settings/developers
Click on the OAuth application you setup for Cloudflare Access to edit it.
In the field that says Application Callback URL, input your authorization domain followed by /cdn-cgi/auth/callback. It will look something like https://dani.authcloudflare.com/cdn-cgi/auth/callback.
Click update application.