Both nostr:npub1ye5ptcxfyyxl5vjvdjar2ua3f0hynkjzpx552mu5snj3qmx5pzjscpknpr 's and Stu's implementations forward GET requests (302 Found) to external blob storage services, i.e. the request is served by those services that DO support range requests.
I have tried to implement range requests with my cloudflare worker based solution and have still some bugs/issues.
Downloads (GET) with ranges are covered well by the HTTP spec. IMHO it could make more sense to put a multipart upload API in the blossom spec to support large files.