Set default-terminal and terminal-overrides to $TERM

[realguse]

Sensible should set the default-terminal and terminal-overrides to the $TERM environment variable.

The reason for this is that you should not change the $TERM variable, its your terminal emulator that assigns it. For example, if you use kitty, it would probably be xterm-kitty, and for alacritty it would just be alacritty.

set -g default-terminal "$TERM"
set -g terminal-overrides ",$TERM:Tc"

[MartyMcFlyInTheSky]

I just noticed that and I agree. I do set these options in the beginning, I don't like sensible to overwrite it. The way OP proposed is the correct way to handle true color terminals (or any).