Another work occurs to me as possibly belonging to the sub-genre: The High Crusade by Poul Anderson. It relates the tale of a group of medieval knights & men-at-arms taking to the stars.
That's SF set in the past, not fantasy set in the future. I don't remember the details but, however logistically implausible, other than the usual FTL, I don't recall anything making it purely, strictly fantasy. 'Course, my memory is generally poor.
But this is getting bogged down in the perpetual indecision of "what is
genre x?" and the OP never clarified what he meant.
As possible items that might fit, maybe stuff like Kuttner and Moore's
Earth's Last Citadel and some of their other science fantasies might qualify, but these were written as being loosely understood to be science fiction - they both wrote outright fantasy
[1] and these aren't that.
Also, I think Cherryh's Morgaine saga would qualify if the background was important though the foreground is pretty thoroughly fantasy-like.
Silverberg's Majipoor began as definitely a very thorough blend of fantasy-feel and SF elements but I understand it became more fantasy oriented as it went on (I was satisfied after the original 3, so I'm not sure). That might qualify.
If you treat Goldstein's
The Dream Years as a fantasy (a story with time travel about surrealism), some of it is set in the future, at least.
Some of Tanith Lee's "SF" might be better read as futuristic fantasy, such as
Day by Night.
Some Zelazny is heavily fantasticated, though usually billed as SF with genuine SF elements.
And, yeah, much of PKD. And some Sturgeon. And if we're including Harness, we have to include much of van Vogt.
Star Wars might be the definitive example, though the Force is probably more plausible than the spaceships.
But it's kind of impossible to cite useful examples without clarification of what we're supposed to be giving examples of.
[1] Or at least Kuttner did - seems like most Moore is always mixed with some vague touch of SF at the least - I think "alternate dimensions" tend to be SF handwavium more than fantasy and I think those even occur in Jirel.