The Maxmind GeoIP database has a connection type field to determine if an IP is mobile or fixed so could use that as part of the decision. https://www.maxmind.com/en/geoip-databases
Something like Akamai does with some of their CDN products:
https://techdocs.akamai.com/property-mgr/docs/adaptive-img-comp-aic
It looks like they have some sort of logic on their edge servers to detect network type and also use the latency to determine if images should be compressed.
Discussion
Both are not really feasible, for something that makes no money from serving content, unfortunately. 🐶🐾🫂