Can you try now, it should be working as always. What kind of cache? And why do you need cache when we already have one and it is on CDN and used by many? In general, any extra caches do more harm than help, fragmenting caching, disallowing fast deletion, killing any sort of access counters (users want that), and potentially corrupting the media before it is delivered to the user. We already serve thumbnails (nip94) has it all in all different sizes and formats.
Discussion
The proxy is there to protect user IP addresses from suspicious image hosts. I could maybe special case nostr.build, but that way sort of lies madness
Doing proxying is where lies all sorts of madness, since now you are subscribing yourself to hosting of potential CSAM and doxxing people in photos/videos since we are unable to signal deletion to you. Also, posting a link to anything that is not media, may prompt browser to prefetch its content and disclose IP address. If people want to protect their IPs, they should use TOR (or at worst VPN), otherwise you are doing proxying for the wrong reasons
I get that. There's also the optimization side of things; imgproxy also saves a lot of bandwidth on mobile connections. I don't see a real solution to the dilemma