Sounds like you made it harder than it needed to be: from any web browser, even the one on your phone, navigate to your hub's admin interface (e.g., just type in the IP address, or use Portal to find it if you haven't made a static/reserved address). Then click or tap "Apps" on the left--not "Dashboards"--and find Hubitat Dashboard in the list, which should have all your dashboards listed under it. Open the one you want, then copy either then "Local LAN Link" or the "Cloud Link" (obviously want cloud if you're using it away from home).
In the early days, this is the only way we had. Adding the "Dashboards" menu item on the left made them easier to get to but more confusing to explain how to get the URL, and the mobile app doesn't do anything special here besides help you get to something exactly like that.