Hi Aen-Sedhe welcome to the boards!
I'm a big fan of the precursor civilization and alien "magic is really their science" tropes too. Adventurers are sure to encounter bits of alien tech and remnant advanced populations in their travels. But there's not enough of it to reverse engineer or help advance civilization out of the dark ages. So, my personal preference is much more than Howard's Conan, much less than He-Man or Thundarr. Roughly around Arneson's Blackmoor 

I'm trying to add more and more, but that really isn't saying much.

As much because I'm trying to make a weird scientist class  as finding a fun way to do it.

I even have tech from other eras like weapons used by a WW2 Ranger platoon.

Most recently I introduced one of my campaigns very briefly to my Warp Rider idea.

Swordfish Island from Echoes of Fomalhaut #3 I improvised some alien tech. The players haven't really investigated them yet. I can't recall if I detailed here those. Largely inspired from "The Lost Room" series.

I liken the "Wierd Science" portion of Hyperborea's setting to Ancient forgotten technology and Alien (Ancient Gods) tech. And placement should be not unlike Expedition to the Barrier Peaks from the original D&D. Once in a long while characters may come upon an ancient ruin where technology could be located. but not often, and limited (don't want to go full-on Monte Hall on them, as it's then hard to reign back in). 

For example, in something I'm writing up, I have two locations of technology (of about 8 active locations) One is an ancient Atlantian Pyramid that is actually a Prison, and another is a tower of an Ancient Atlantian Mage (now a Lich), and he has some remnant technology.