There are alternatives to 100% canvas. A 50:50 blend of polyester and cotton is an option. I used cheap canvas painters tarps for the wall of my yurt and they are that blend. Porous as all get out but have held up better than the 100% cotton canvas roof cover. I left a post on your other thread about 'My Tarp'.
Other materials. Sunbrella, which is a synthetic material that is used for boat covers. Beats me how long that's gonna last. Painting a straight canvas tarp might be the best idea. Just a guess though never done it.
If I was planning on living in my yurt full time, I'd either buy a 15 year cover from a professional yurt manufacturer, or redo what I did with the canvas tarp, but paint it with 50:5 paint water ratio.
trapped inside a drafty yurt like mine ain't gonna happen.
That's all I have. Good luck.