one year ago, i install on my a1200/060 + mediator/voodoo3
debian3.0 (if i remember correctly) (68k version of course)
But in past time, we do not have any video drivers for a1200 mediator (for a4k as i remember somebody was wrote driver for voodoo). So, i try it on aga. (framebuffer was supported too). Console browsers like a lynx and a links work perfectly of course

(textmode) That about x-window - i setup it in 256 colors on aga, and run netscape

it's work but, too slowly. (but work

If anybody will write driver for a1200 mediator/voodoo3 - i think it will be fast. (maybe driver was writed for present time?)
take a look here for example:
http://people.debian.org/~cts/debian-m68k/woodyand here:
http://www.linux-m68k.org/debian-amiga.htmlcpu version does not matter for it, just downloading 68k version, and installing (install.txt or readme.txt can give you way of installation).
btw, it was work really stable for me. But as i know debian not supported amiga now, so maybe best way try to NetBSD ?