I wrote a cross-platform open source texture viewer. It's still WIP, but already supports 2D textures and cubemaps in DDS, KTX and KTX2 formats and normal image files that are supported by stb_image (JPG, PNG, BMP, TGA, ...).
It allows viewing mipmap levels, also next to each other (for 2D textures).
All in a single small (<3MB) executable.

A first release is available (binaries for x86_64 Linux and Windows): github.com/DanielGibson/texvie

0

If you have a fediverse account, you can quote this note from your own instance. Search https://mastodon.gamedev.place/users/Doomed_Daniel/statuses/114246146191096582 on your instance and quote it. (Note that quoting is not supported in Mastodon.)