tmux: Add conditional for old tmux

.tmux.conf

@@ -18,7 +18,11 @@ set -g default-command "exec /bin/zsh"
 
 # Enable Truecolor
 set-option -ga terminal-overrides ",xterm*:RGB:Tc,rxvt-unicode*:RGB:Tc"
+%if '#{>=:#{version},3.2}'
 set -ga terminal-features ",alacritty*:RGB"
+%else
+set -ga terminal-overrides ",alacritty*:Tc"
+%endif
 set -g default-terminal "tmux-256color"
 
 # Make M-<up> and so on work in Emacs.
@@ -40,8 +44,7 @@ set -g mouse off
 tmux_colour_status1="colour61"   # violet
 tmux_colour_status2="colour97"   # dark pink
 tmux_colour_inactive="colour237" # dark grey
-# NOTE: Prefix with %hidden since 3.2, but can't figure out how to do
-# conditionally. Correct %if still complains.
+# %hidden does not work with < 3.2, even if it's not accessible
 
 # Status line
 set -g status-style fg=${tmux_colour_status1}