But in the fantasy realm you're right I can't think of anything since Skyrim off the top of my head thats open world AND first person.
Metro is about as on-rails as you can get? It's all "go down this one tunnel and shoot everything" or "follow this actually quite narrow and linear path across the rubble and shoot everything". Some of the missions are literally on rails (you're in a subway, after all)
Far Cry is much more open than Metro, and often has some quite fun things to do if you stray off the mission path and talk to the right person. Depends how much you like to hunt and fish amidst blowing up the bad guys!
I'm not sure I'd call Far Cry series RPGs. Don't mean that in a bad way (I fuckin love Far Cry), I've always seem them as an FPS with stats (a la No One Lives Forever) in an open world.
I really wanted to like The Outer Worlds, but the writing seemed extremely juvenile; it touches on a lot of heavy themes (LGBTQ romance, corporate power, worker exploitation) extremely hamfistedly and without nuance. I had to put it down as I couldn't stop cringing at the writing...
Now, Outer Wilds on the other hand...