Why would you think Raspbian would even work? Does the Orange Pi use the same Broadcom SoC as the RPi series? If not, chances are very slim it would even boot, let alone provide you with a useable display or serial driver. (Just because they're both ARM processors doesn't mean anything, because Raspbian only contains kernel drivers for RPi hardware.)
Raspbian is a Raspberry Pi specific distro of Debian. Hence the Rasp in Raspbian.
When they say compatible with the RPi2, I would assume they mean from an I/O perspective, i.e., it has header with the same pinout as the RPi2, allowing you to use existing RPi add-on boards ("Hats").
Do you know what kind of SoC it uses? I'm sure it's a common one. If so, there's a good chance Debian or Arch ARM will run on it. (In the case of Debian, you only need to download the ARM7 build, it will load the correct kernel drivers on startup for you. For Arch ARM, it's a bit tricker, depending on your hardware, but their site should have instructions.)