I'm unsure if this will help, but the new image format JPEG XL (.jxl) is coming soon to replace JPEG. It will have a lossless and a lossy abilities. It claims to be faster than JPEG.
Another neat feature is that it's designed to be progressive, so you could host a single 10mb original file, and the client can download just the first 1mb (up to the quality they are comfortable with).
This is a research university that moves very slow, so waiting two years for something better is actually a possibility (and prerendering to S3 works ok for now). I'll keep this bookmarked.
Another neat feature is that it's designed to be progressive, so you could host a single 10mb original file, and the client can download just the first 1mb (up to the quality they are comfortable with).
Take a look: https://jpegxl.info/