Hey! It's me again who tried to help you yesterday or earlier today with the long message, or at least try haha.
It didn't let me respond to your message so figured I'd just leave another review.

Anyway, I just realized how dumb I actually am. I didn't realize the add-on would create another sub-menu in your context menu when you right click on an image!!
I saw the "Convert and save your images as" add-on feature! I feel like this should have been obvious for me but for some reason I went straight to the normal "Save As" and I thought it would automatically convert images from there to .png and .jpg.

So maybe others are running into the exact same problem I did and didn't realize there was another menu for it haha. At least I think so.

But yeah, right now, extension works perfectly so far!
However on Twitter it seems like when you try to save an image using the extension you have to type in file extension manually. Reddit and Facebook it seems to work fine though!
Here is the Twitter image I tried to save, but I think it happens pretty much with any Twitter image
https://twitter.com/sylvainsarrailh/status/1388105998011875330/photo/1

I am going to guess where people had this problem the most in my opinion was maybe Reddit, it's so far the only place where I saw it saved images as .webp.
Twitter and Facebook by default saves the images in .png or .jpg when you do the original Save As way.
Unless of course you need more help, then I won't leave another review haha.
But yeah, good luck and keep up the good work!