diff --git a/debian/configure b/debian/configure
index c960e40050c..109c1af9842 100755
--- a/debian/configure
+++ b/debian/configure
@@ -1,6 +1,7 @@
 #!/bin/bash
 # dpkg configuration script for linuxcnc
-# Copyright (C) 2006 Jeff Epler
+# Copyright (C) 2006      Jeff Epler
+#               2025-2026 Steffen Moeller
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -12,6 +13,32 @@
 
 set -e
 
+if [[ -z "$OSTYPE" ]]; then
+    echo "E: The 'OSTYPE' environment variable is not set."
+    echo "   Failure to confirm Linux as the operating system cannot be determined."
+    exit 1
+else
+    echo "D: Found operating system '$OSTYPE'."
+    if [[ ! "$OSTYPE" == "linux-gnu"* ]]; then
+        echo "W: LinuxCNC is not (yet) prepared for the operating system '$OSTYPE'."
+        if [[ "$OSTYPE" == "freebsd"* ]]; then
+            echo "   For FreeBSD there have been reports for LinuxCNC to compile and be executable."
+        else
+            if [[ "$OSTYPE" == "darwin"* ]]; then
+                echo
+                echo "   LinuxCNC is yet unlikely to be successfully built on MacOS because of missing dependencies."
+                if command -v brew &> /dev/null; then
+                    echo "   With brew, we are aware of packages"
+                    echo "     autoconf automake libusb libmodbus libtircp pkgconf"
+                    echo "   but missing is, e.g., a package for libgpiod."
+                fi
+            fi
+        fi
+        echo "   Instead of this Debian+derivative-tailored configuration please invoke the compilation directly."
+        exit 1
+    fi
+fi
+
 usage () {
     P=${0##*/}
     cat 1>&2 <<EOF