It’s not just gapps, though. Search, gtags/adsense, youtube, maps, etc are all so pervasive that google effectively controls the internet. You can try run ublock and a plethora of privacy addons, but those are only effective as long as Google is playing nice. Others, like Yandex, are not, and they defeat all those with ease.
Though I’d say running custom rom is an exception from the rule, along with people running with dumb or even no phone, but those are not but a blip on a big picture.
Just checked, our very corporate and much antiquated website does accept apng (sadly not publicly visible as it’s b2b only). We do deal with photography though, so we do expect multitude of formats and mostly either pass them unchanged or just feed them to ImageMagick and forget about it. The bane of our existence is mostly DNG which Adobe breaks every year or so by introducing breaking spec changes.
EDIT: Haven’t found a place to even get an mng sample, though. Do you have any?