Installing incompatible ROMS I was wondering if you are able to install ROMS, for example, the Ubuntu Touch OS for the GS2 i9100 onto the GS2 SPH-D710. Will it brick my phone?
In general, no, it is not possible to flash ROMs made for a different model.

Specific to your device, no.  Flashing ROMs for the I9100, I9105, I9100G, I777, and T989 on you device will result in you having a phone-shaped paperweight.

You can find appropriate ROMs for your device here, among other places.