I have my own wallpaper too; Steve and I are talking about the boot-up screen, with the garish artsy picture.Oh, I already have a desktop wallpaper (one of my own images) that I use for both my computers and when I updated to Big Sur (just did the update, didn't do a "clean install,"), there was no hassle in it automatically being set up right from the get-go so that I immediately felt "at home" with Big Sur before even doing anything in it.
I tried editing with Photos, another learning curve and it wasn't intuitive to resize a batch of them.I have had the same issue with crashing on attempts to export from Luminar 3, too. Editing works just fine and everything looks great until I hit the button to send the newly-edited file back to the desktop. I have heard that the same issue affects Luminar 4 as well. Someone suggested that a workaround is to instead export the image to Apple's Photos app and then one can do with it as desired. I haven't tried that and I have no idea of the same solution would work with NX-D, but it might be worth giving it a shot. As for Nikon's software, I'm like Nick, I haven't used it for years ever since I had issue with some version of it. I decided it wasn't worth messing with and never installed it any of my machines again.