I selected fall in the park wallpaper because I loved the dynamic nature of it last year, but it does not appear to be dynamic anymore, and I can't find any wallpapers that are. Has @RokuCC Roku stopped supporting dynamic wallpaper on Roku Streaming Stick (3600 series)
I'm still using my all time favorite "Graphene" wallpaper on the 3600, but it's no longer available to download so I don't want to switch to something else to try for fear I can't get this one back. I already learned that lesson on a 3810.
On my 3810 I seem to remember some of the "Featured wallpapers" at Settings > Themes > Wallpapers had some dynamic elements (blowing leaves, etc) but the couple I tried looked static.
Additional response:
I checked on my two other Rokus, a Streaming Stick 4K+ 3821 and TCL Roku TV C107X. On both of these, 5 of the wallpapers listed as "Featured wallpapers" are labeled as "Dynamic" and do have animated features. These same wallpapers on the 3600 and 3810 have no such labels and are completely static.
So it's not just me that it's happening to then. There used to be dynamic wallpapers on that device. What's weird is that my older Roku Express still has them, along with my favorite "Roku Daydream" that isn't available on newer/nicer models that I've seen.