PiMiga is a fairly popular ready-made Amiga distro for RPi, based on modern-look Amiga OS, and full of assorted bells and whistles, plus the usual set of demos/soft/games/modules/etc. The guy who made it (?) is porting it to MiSTer currently.
I'm more of the old-school OS fan myself, but I know this kinda setup has quite a few fans, so if you're interested you might want to keep tabs on his utube channel. He says there will be a beta release around Xmas.
