There is no Android P beta, not even from Google. The developer preview is a long way before beta and not intended or suitable for general use. It is intended for use only by developers (Android developers, app developers, and web developers). If you are not a developer (or equivalent), you should not be attempting to use it. Distribution only via flashing is a non-issue for the intended audience; OTA is not needed.
Update: it is now working, I used opera to access the page, put in your first IME number and network provider to enable you download the package in .zip file, not that you need the latest Android adb to initiate this installation.
And Yes, I am a developer, that is why I'm testing my apps on the A P beta. (To whomsoever it may concern)