Here's another possibility that just cropped up on DTRPG - A Voyage To Fomalhaut. Says its for OSRIC and may not be wholly systemless (there a couple of gold piece costs mentioned in the preview) but it also appears to be mostly a proper gazetteer for a sword & planet setting with a bit of the vibe Tekumel has - degenerate colony world, partially terraformed long ago, post-interstellar collapse and a bevy of new "gods" of various origins. Worth a glance, anyway.
I've learned the hard way to do my campaign worlds systemless. I'm in the process of updating my personal home campaign world book (Amberos/The Dark Summit, replacing art and updating entries), but it's not ready yet. It's a kitchen sink fantasy world, but I have put a lot of work on it.
However, on DriveThruRPG I have Crimson Empire. It is a quasi-Arabic realm whose main kingdom (Eth-Authuram) stretched the continent until it was blasted by magical catastrophe. It is in the process of recovery, but is abound with city-states and break-away states trying to make their own way forward.