Most solutions mentioned below will require your tablet and computer to be on the same Wifi network. And choosing higher resolution for your external display (tablet) usually will lead to more latency although usability is still quite good.
I've arranged the solutions below according to pricing (free to paid) and whether there's a need to purchase hardware.
Personally, I'm currently using Spacedesk. I actually have the Luna Display adapter but I could not get it to work on my Surface Pro 8 and Huawei MateBook D 16.