So I got a N950 from Nokia, flashed it to beta2, but I cannot enable developer mode.
Every time I try, and confirm with OK, then accept the dependency notice, it then immediately says
Download failed
developer-mode
Can't complete the download.
Connection do the application provider was lost. Try again later.

And Try Again does the same.
I have tried many times, as well as rebooting, enabing installing apps from non-store locations, updating the applications (apt-get update I guess) and trying again on a different day and time...

Without more information in the error message, and without a terminal (catch 22...), I can't find out what it's trying to download exactly, to see if it actually exists..