Go to nikonusa.com and purchase a refurbished Nikon D850... especially when they offer an additional 10% discount, usually around holiday times... Memorial Day, Fourth of July. Alternately, buy a refurbished Nikon Df from the Nikon web site.
I live in a smallish apartment in Manhattan with limited storage space. Instead of storing four oversized LowePro camera bags in a corner of my living room, I purchased a Slinger Electric Dry Cabinet for lenses and cameras. Now all of my lenses are in one place and displayed in an attractive humidity-controlled cabinet. And my wife is much happier.
Wonderful camera and it must have great memories.... Would be fascinating to know on the Nikon F's 50th anniversary where it has traveled and what it has shot over the past 50 years!
To me, the term "nifty" should be limited to a 50mm "pancake" lens that is unobtrusive and can be carried around in your pocket. I have a Nikkor 50mm f/1.8 Series E AI-S manual focus pancake manufactured in Japan from the early 1980's that I use on my Nikon Df and D850. It's not only "nifty," but it's also "cute as a button" ... and takes good photos.
I'm in the same boat as you with a D850 and iPhone 12 (except instead of the D500, I have a Nikon Df)... Keep your two "real" cameras as well as your iPhone 12 for convenience in emergency photo opps, and save your money.