Parece que na sua linha 13, shadow-exclude = [ não tem um colchete de fechamento, apenas comentaria essa linha
compton.conf não funciona no ubuntu | XFCE
* eu fiz uso sample.conf e algumas configurações de amigo
abdipn@indoxploit:~$ compton --backend glx --config ~/.compton.conf
Erro ao ler o arquivo de configuração "/home/abdipn/.compton.conf", linha 45: erro de sintaxe
# Shadow
shadow = true;
no-dnd-shadow = true;
no-dock-shadow = true;
clear-shadow = true;
shadow-radius = 5;
shadow-offset-x = -7;
shadow-offset-y = -7;
shadow-opacity = 0.7;
shadow-red = 0.4;
shadow-green = 0.4;
shadow-blue = 0.4;
shadow-exclude = [
# "! name~=''",
# "name = 'Notification'",
# "name = 'Dunst'",
# "name = 'Plank'",
# "name = 'Docky'",
# "name = 'Kupfer'",
# "name = 'xfce4-notifyd'",
# "name = 'dmenu'",
# "name = 'dmenu_run'",
# "name *= 'VLC'",
# "name *= 'compton'",
# "name *= 'Chromium'",
# "name *= 'Chrome'",
# "name *= 'polybar'",
# "class_g = 'Conky'",
# "class_g = 'Kupfer'",
# "class_g = 'Synapse'",
# "class_g ?= 'Notify-osd'",
# "class_g ?= 'Cairo-dock'",
# "class_g ?= 'Xfce4-notifyd'",
# "class_g ?= 'Xfce4-power-manager'",
# "_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'",
# "_GTK_FRAME_EXTENTS@:c",
# "!focused"
#];
# shadow-exclude = "n:e:Notification";
# shadow-exclude-reg = "x10+0+0";
# xinerama-shadow-crop = true;
# Opacity
#menu-opacity = 1;
inactive-opacity = 1;
active-opacity = 1;
frame-opacity = 0;
inactive-opacity-override = true;
alpha-step = 0.06;
inactive-dim = 0.1;
inactive-dim-fixed = true;
blur-background = true;
blur-background-frame = true;
blur-method="kawase";
blur-kern = "3x3box";
blur-strength = 5;
blur-background-fixed = true;
blur-background-exclude = [
"window_type = 'dock'",
"window_type = 'desktop'",
"_GTK_FRAME_EXTENTS@:c",
"class_g = 'firefox'",
"class_g = 'Firefox'",
"class_g = 'qutebrowser'",
"class_g = 'feh'"
];
opacity-rule = [
"80:class_g = 'URxvt'",
"80:class_g = 'Gnome-terminal'",
"85:class_g = 'Nautilus'",
"85:class_g = 'Thunar'",
"85:class_g = 'Transmission-gtk'",
"0:_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'"
];
# Fading
fading = true;
# fade-delta = 30;
fade-in-step = 0.1;
fade-out-step = 0.1;
# no-fading-openclose = true;
# no-fading-destroyed-argb = true;
fade-exclude = [ ];
# Other
backend = "glx";
mark-wmwin-focused = true;
mark-ovredir-focused = true;
# use-ewmh-active-win = true;
detect-rounded-corners = true;
detect-client-opacity = true;
refresh-rate = 00;
vsync = "opengl-oml";
# dbe = true;
paint-on-overlay = true;
# sw-opti = true;
unredir-if-possible = true;
# unredir-if-possible-delay = 5000;
# unredir-if-possible-exclude = [ ];
focus-exclude = [ "class_g = 'Cairo-clock'" ];
detect-transient = true;
detect-client-leader = true;
invert-color-include = [ ];
# resize-damage = 1;
# GLX backend
glx-no-stencil = true;
# glx-copy-from-front = false;
glx-use-copysubbuffermesa = true;
glx-swap-method = 3
glx-no-rebind-pixmap = true;
# glx-swap-method = "copy";
# glx-use-gpushader4 = true;
# xrender-sync = true;
# xrender-sync-fence = true;
# Window type settings
wintypes:
{
tooltip = { fade = true; shadow = true; opacity = 0.75; focus = true; };
};