This will make me be detected as a bot and I see captchas everywhere afterwards. I was using that for a while.

A better alternative would be content identity through URLs.

If your marketing page is at github.com/index.html, then make something like github.com/dashboard.html for logged in users, and redirect them to /login.html when they are required to be logged in.

This way users can easily bookmark the page that they actually want to see.