If uzdoom is installed then prefer it over gzdoon.

goat/gzdoom.py

@@ -1,9 +1,12 @@
 import os
 import subprocess
+import shutil
 
 from . import util
 
-GZDOOM_PATHS = []
+GZDOOM_PATHS = [
+    shutil.which("uzdoom")
+]
 SLADE_PATHS = []
 GZDOOM_PROJECT = "iwadinfo.txt"
 
@@ -19,7 +22,7 @@ class Project():
 
 def find_gzdoom_command():
     for exe in GZDOOM_PATHS:
-        if os.path.exists(exe):
+        if exe and os.path.exists(exe):
             return exe
 
     return "gzdoom"