Nomadic Mongolians have lived in gers for many centuries. I've read that they typically move three to four times a year. They literally move their 6 meter (average)yurt in a day or two with truck or van nowdays. FWIW, in the nomadic yurt vids and pics I've seen online the ground is left uncovered, or possibly covered with rugs. How accurate a statement that is I'm unsure. Unless you get first hand info it is just a guess.
I've also seen on YT a video of young nomadic couple living in wet northern Europe, erect their yurt atop a poly tarp, as I detailed above. Apparently a tarp on the ground works for them. It is covered with rugs. They can also move their yurt in a day using a vehicle for transport.
In fact, if I lived a nomadic life, and wanted to save my money,- and hassle- I'd probably also erect my yurt atop tarp. A tarp is cheap, effective and a snap to install. Just roll it out on flat ground , erect the yurt and secure the tarp under the wall cover. Voila! Waterproof bathtub floor. Good for keeping
off the floor coverings, bugs from emerging into the yurt.
If I had to pick between my present yurt-the one on the platform in the back yard- and another one set atop a tarp, I'd of course pick the one on the platform. Until I had to leave, that is. And that's the point of all of this.
None of my ideas- gravel, 4x4s, boards etc. is nomadic. A tarp, now that IS nomadic.