I went with chafa as it's terminal agnostic and supports various modes.
Then again, I'm not really sure a tui frontend needs high quality image rendering. Earlier I even considered going completely 1bit braille or just ASCII just so that the image doesn't take all of the focus at the expense of the post body.
As mentioned by another commenter, I believe opening the full image in an external viewer is a much better solution, not to mention easier to implement.
A quick research tells me that there aren't patches for other emulators, but the protocol seems well described, so making those patches is possible.
I could also take a look at Alacritty source code and deicide if I could make this project work.