How do I install Plasma Active on a Galaxy S II (GT-I9100)?

I think nobody has tried to dual boot in Galaxy S II. There are other ARM based systems where Plasma Active run on:

http://community.kde.org/Plasma/Active/Installation

The instructions in "1.2 Deploying a Plasma Active (MMC) raw Image to a MultiMediaCard" is for Nokia N900 and installs the PA to a MMC card, not the internal memory (so the Android installation remains intact). Maybe that works for you, but again, nobody has ever tried that with Galaxy S II as far as I know. If you are unsure do *not* try it. Anyway, if it works the system will run very slow because MMC is slower than the internal flash memory.