While setting up a new gallery thingy (changes on caption and stuff), I also tried to implement WebP-images … but: It didn't work.
First I thought the path settings may have changed and manually fed an url to an image … didn't work either.
In search for a solution I stumbled upon this discussion: viewtopic.php?p=350197&hilit=webp_image#p350197
However, in my case I just simply call the very regular gallery url, which is like ...blabla.com/gallery/tag/38.html just how the gallery module generated it - no fancy JS, no delayed loading, no tweaks in the gallery module or whatsoever else I'd know of.
However, that "( $_SERVER[ 'HTTP_ACCEPT' ], 'image/webp' ) !== false)" from that discussion I just mentioned stuck with me.

So I copied that php-file and started commenting out all those conditions (lines 55, 75, 79, 81, 82, 83) — and NOW the magic happened!

But now I'm just puzzled why - and I very much dislike the fact that there's no fallback, altho meanwhile every browser should accept WebP?
Still, not a good thing. But: WHY is this?
And I very much remember, that this very plugin HAD worked with an other page - and I just checked it and it also now serves only the original jpg-source files (all the webp-files are still in the tmp/cache/ folder tho).
So, something must've happened since whatever the latest CMSms releases or PHP update (I'm on 8.1).
Do you have any ideas?
Thanks!