Look into a 45mm PC-E and an 85mm PC-E. Wide and ultra wide lenses can't compare to longer lenses especially if you do stitched panoramas, which is a very common practice for many digital photographers who shoot landscape.

Here are some examples of panos taken with longer lenses:

https://www.flickr.com/photos/gene_lugo/albums/72157687713807602

You don't need a wide angle lens and all the negatives associated with using a wide lens (keystoning, perspective extension distortion, volume deformation, having to crop out lots of sky and foreground, etc. You can pick your angle of view, and make it as wide or narrow as you like. Many of my mutli row panos exceed 150mp - or more than three times the resolution of your camera.


Or you can just follow what all the others do and use an ultrawide lens to "get it all in" which usually means lots of width and lots of sky and lots of foreground and lots of perspective correction and cropping - good thing you have 45 mp to work with.

Wide and ultra-wide lenses are specialized, suitable for just a few kinds of images, and ought to be used with discretion. Otherwise you will end up with stuff than looks like everyone else's wide angle shots. A good landscape should show things in proper perspective, and without the all-to-common effect of huge foreground elements and teeny tiny everything else. I have a 14-24, which is an excellent lens, but it really only gets used for about 5% of my images. And I do a lot of landscape.

This is a little like asking "What is a good breakfast food?" Do you lean toward eggs and "bangers" or something light like fruit and a croissant? Something sweet like French toast or Belgian waffles?
As a "fellow" landscape shooter, I prefer to try for "The grand landscape." I mostly use wide-angle lenses. I say "mostly" because now and then I put on my 200mm eyes and like to pick parts of what I see. Maybe you could provide us with just a tad more info as to what your preferences for a landscape are.

I like my tamron 17mm spII (an old manual focus lens) but I also like my 20-35 f2.8 AF. they are both very sharp. If I had the money for the 14-24, I would consider it, but would want to shoot it first. I would also consider nikon 16-35... there is no magic lens, just one that does what you want it to on your D850. When i got my 850, I was told that I would have to replace all of my glass as the D850 was so demanding... (salesman said that...) he was looking to sell glass. I shoot a lot of older high quality glass, and the D850 does very well with them. just decide what focal length you want and then rent/barrow/test a few lenses in that range and you will know what you want! I can tell you all day what is my favorite, but you may not like it for one reason or another... I know that a lot of people love the 18-200 nikon... I bought one and hated it, but everyone told me how great it was, so thinking that I got a bad copy, I bought a second one... I should have saved my money and bought a real lens... that is how our opinions can very and yours will as well. try some out!
kelly