TMUX how to enable 24-bit true color support?

Question

Arch Linux

Good afternoon!
OS : Manjaro Linux with KDE
tmux : fresh master branch
Shell : zsh
External tmux

$ echo "$TERM"
xterm-256color-italic

In .zshrc

export TERM="xterm-256color-italic"

In tmux config

set -g default-terminal "xterm-256color-italic"
set-option -ga terminal-overrides ",xterm-256color-italic:Tc"

Inside tmux:

$ echo "$TERM"
xterm-256color-italic

I suspect that the problem is in redefining the settings of the wrong terminal, because.

tmux info | grep Tc
202: Tc: [missing]

From outside tmux, tk-colors work fine in the terminal. in it - no.
I ask for advice.