That certainly sounds like you're really needing an upgrade for what you want to do then.
Even trying to get a GTX 2060 is a nightmare.
I've seen AMD 5600 and 5700s plenty.
The absolutely beast of a content creation machine, IMHO, needs an AMD Threadripper. Expensive as hell, but you're guaranteed to find one.
I think if you're willing to spend that much on a machine, you can probably get all the parts you want (minus an AMD 5900x or 5950x and a GTX 3090), and then buy a prebuild with a GTX 3090. You could salvage the card, RAM, power unit, hard drives, and case.
You may need to do a fresh install for Windows. Buy the CPU, motherboard, GFX card, cooling.
Or, you can save the hassle and buy that PC you posted. It's a beast. You got me envious already.