The verses are in G minor, and the pre-choruses and choruses are in A major; the bridge is in Bb major and then the song ends in A major. Weird but smooth transitions.
Do you know of any other songs by other artists that change keys into the tritone? This track has verses in E major, choruses in G major, and a coda in Bb major.
Would psychedelic metal from the late 1960s possibly count as proto shoegaze? I was thinking some of the noisier Velvet Underground tracks. I also had in mind a couple of Beatles tracks (It's All Too Much has the spacey vibe but it's not all electric.)