Sometimes, it's advisable to just smile and nod

Have found it impossible to upload this file directly to Lemmy. It's already a compressed WEBP file, but whatever settings I use, Lemmy insists on copying it and compressing it further, until there's only about 5 pixels left. So the only options left are for the post to be a link to the external url, or for it to look like a comment post, but with an inline image squashed inside. Neither are ideal.

EDIT: My experience with Lemmy:

EDIT 2: Now have something a bit more acceptable, loaded directly to Lemmy.
Lemmy always seems to compress WEBP at 75% - I uploaded an image, it compressed it, I downloaded Lemmy's version and re-up'd that, and it compressed it again. Presumably I could do this forever.

So, I created the original WEBP using the 'lossless' setting (it was about 2.5MB), uploaded that and let Lemmy convert it, and now it doesn't look too bad. The only thing is I had to use the version I tested at enterprise.lemmy.ml, 'cos feddit.nl got confused by the transparent frames. So the trick seems to be: upload the least efficient version imaginable