Looks like you’ve gotten some things figured out. Good stuff.
I think the Android app is defaulting to a “sitemap” which is a legacy interface from openHAB 2. If you open the left-hand menu, you should be able to choose “openHAB 3 UI” to see your “Overview” page.
You can change the default in the settings by going to “Display” → “Start page” and choosing “openHAB 3 UI”.
I feel like there was a discussion about changing the default, but that might still be in the beta version of the app.