Youtube screenshot as wallpaper on Ubuntu 20.04?
Solution 1:
Check the resolution of your screenshots, and then check the resolution of your display. You will probably find that your display has a much better resolution than your screenshots, so the screenshots need to be scaled up when used as background images.
Videos tend to use very aggressive compression methods to keep the size of the data transfer down. It doesn't matter much as long as there is motion; the human eye and brain don't catch that level of details during motion. But when you pause the video and look closely, you will see those compression artifacts; it's not anyway close as detailed as an image taken by a stills camera.
It may work to some extent to use very good 4k footage as a base for a background image on a full HD (1920x1080) display, but even full HD video for a full HD monitor is stretching the limits; even more so with YouTube's very aggressive video compression (they want to keep down bandwidth).
In general, it's not a good idea IMHO.