You can throw almost any image format with open standards into squoosh.app if you're still using software that doesn't open webp.

It's been a while since Photoshop finally got support, though, I can't recall the last time webp posed a problem for me. Then again I don't use a Firestick, no idea how that would deal with image formats, I guess it's no longer being maintained?

No the firestick reference was for video formats.

H265 for example. Or Dolby Vision.