@ZogStriP There is a library that can do this client-side, see https://github.com/alexcorvi/heic2any for an implementation but this seems considerably trickier. Heic2any does not retain metadata, which makes it less useful for converting files at upload. The library maintainer suggests it be used for display purposes only. But, while storing HEICs is more efficient (better compression), it would complicate lots of things in our upload pipeline, since HEICs aren’t recognized as images (no thumbnail or optimized image generation, markup would need to be converted from an attachment to an image, etc).
Also, the client-side library is quite large, at 1.15Mbs minified.