Rather than covers, for many years I’ve enjoyed using Emmerson Gray’s felt sleeves (
https://www.emmersongray.co.uk/) when I travel and need to carry my reader in a backpack or suitcase. The rest of the time, especially at home, I don’t bother with any protection at all. I’ve never had any problems with damage or scratching - these things nowadays are so light and oleophobic/scratch-resistant that fragility isn’t nearly as much of a concern.