Comment by _qbjt

It also seems like support for JPEG 2000 can be hit or miss. I tried to open a .jp2 file I downloaded from the web into GIMP, but it looks all funky.

Original image: https://www.fnordware.com/j2k/jp2samples.html

What it looks like in GIMP: https://imgur.com/a/HCNz7ga