It's under very active development:
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repo.or.cz/w/pyTivo/wmcbrine.git»
pytivo.sourceforge.net/w ··· ReleasesI don't know of any walkthroughs - you shouldn't really need one. Download the latest release and take a look at the read me, it should tell you whatever you need to install. On OS X, it just works. On modern Linux, it either just works or requires a few "apt-get" or equivalent. No idea about Windows.
Then you go to http ://ip of computer:9032/ and finish configuration. At the same site, you can browse through your video files, pick one, and push it to the TiVo.
As for MKVs, I use the
lucasnz branch of pyTiVo. It will automatically convert MKVs into MP4s (with no transcoding if possible) and send the MP4 directly to the TiVo. TiVos don't support DTS, so it will on-the-fly convert DTS to AAC or AC3. I think some of these changes were merged back into the main branch, and it doesn't look like the lucasnz branch has been updated for awhile, so maybe it's time to switch back.