I would at least put it a few inches in the ground. You want to keep the UV light off of it.

You can get the Gel filled wire here: https://www.amazon.com/gp/product/B005EV2A4E/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It's only CAT5e, but it's probably just fine. I'm sure they make CAT6 too.

You can get Biodegradable Anchor Pins here: https://www.dxengineering.com/parts/dxe-stpl-100bd

I made you a video on how some of the stuff works for laying it on the ground. https://www.youtube.com/watch?v=yi2j6qRktrE

Like I said earlier, doing the conduit is the right way to do it, but sometimes just doing this makes sense, especially if you don't want to put a lot of time and effort into it