You shouldn’t put a protector on it. If you get a normal protector, you’re basically just re-adding glare. If you get an anti-glare protector, you’re further increasing the blurriness and darkening the screen, as that’s how anti-glare works. The adhesive will also fill in the etching and reduce its effectiveness (Google “scotch tape frosted glass”, same concept), but how permanent that is has never truly been verified; presumably, a good rub with alcohol should fix that problem.