Kitty graphics can be displayed in tmux via a passthrough sequence and unicode placeholders. This is already implemented by some tools e.g. kitty +kitten icat and https://github.com/sxyazi/yazi
Probably, not directly related, but can confirm the current erroneous behaviour. Another example would be chafa image viewer.
Besides, the present situation (observed in aerc 0.18.2-92) is rather strange: when aerc is running inside tmux inside kitty, chafa launched in
:termdoesn't display anything, while yazi gets stuck on the first image preview. However, when aerc is running in plain kitty without tmux, both chafa and yazi launched in:termjust freeze, and not only by themselves but also to the level that aerc, too, gets to be killed.Just my two cents. Or, rather, tests :) (And, of course, outside aerc both in kitty and in kitty with tmux everything works fine, sorry.)