I want to build LineageOS 15 from source following the titan image build guide which requires the transfer of vendor specific files and thus an adb connection after enabling USB debugging.
I didn't find a LineageOS-specific guide on turning development tools including USB debugging on, so I went with my Android knowledge of tapping 6 times on the build number in the phone settings. This shows a screen with my home screen background and the LineageOS emblem. The emblem responds to taps anywhere on the screen by changing it's styling, but nothing else. I can go back and use the phone including repeating the journey to the emblem screen.
I get that these settings should be hidden for non-dev users and don't need to be reachable very intuitively, but that's covered by hiding the function behind the 6 taps on the version item. After that the proceedure to enable development features can be intuitive again.