worked fine on my android phone, using Connect.

worked fine on firefox & linux, the file shows as .webp to me.

Decided to investigate this a bit: when opened to new window, the image url has ?format=webp query argument, if I change that to ?format=jxl then it breaks as the server actually provides a .jxl file. At least I had to TRY to break it :P

% file c6ca4c8c-20a2-4105-8e6c-833d8c7d3e52.*
c6ca4c8c-20a2-4105-8e6c-833d8c7d3e52.jxl:  JPEG XL codestream
c6ca4c8c-20a2-4105-8e6c-833d8c7d3e52.webp: RIFF (little-endian) data, Web/P image, VP8 encoding, 623x700, Scaling: [none]x[none], YUV color, decoders should clamp