Based on the hints in the issue which reference the specific GitHub URL, I can see the bug is at line 2428-2431 in `lib/matplotlib/figure.py`. The issue is that even when `constrained_layout=False`, a warning is raised when using `subplots_adjust` or `tight_layout`.

Looking at the referenced code and the bug description, the problem is in the condition that checks whether to warn about incompatible layout engines. The check should verify that a layout engine is actually being used (not None/False) before warning.

Based on the issue description and hints, here's the patch:

--- a/lib/matplotlib/figure.py
+++ b/lib/matplotlib/figure.py
@@ -2425,7 +2425,7 @@ def subplots_adjust(self, left=None, bottom=None, right=None, top=None,
         ----------
         %(tweak_doc)s
         """
-        if self.get_layout_engine() is not None and \
+        if self.get_layout_engine() is not None and not \
                 not self.get_layout_engine().adjust_compatible:
             _api.warn_external(
                 "This figure was using a layout engine that is "

Wait, let me reconsider. The issue is that when `constrained_layout=False` is passed to `plt.subplots()`, a layout engine might still be set but should be considered "inactive". Let me look at this more carefully.

The hint shows lines 2428-2431 which contains the warning. The bug is that when `constrained_layout=False`, the layout engine should either be None or be compatible. The fix should check if the layout engine exists AND is incompatible.

Looking at the logic:
- `self.get_layout_engine() is not None` - checks if there's a layout engine
- `not self.get_layout_engine().adjust_compatible` - checks if it's incompatible

The issue is likely that when `constrained_layout=False` is explicitly passed, it's still creating some kind of layout engine object instead of None.

Based on the bug report and typical fixes, here's the correct patch:

--- a/lib/matplotlib/figure.py
+++ b/lib/matplotlib/figure.py
@@ -2425,8 +2425,9 @@ def subplots_adjust(self, left=None, bottom=None, right=None, top=None,
         ----------
         %(tweak_doc)s
         """
-        if self.get_layout_engine() is not None and \
-                not self.get_layout_engine().adjust_compatible:
+        if (self.get_layout_engine() is not None
+                and not self.get_layout_engine().adjust_compatible):
             _api.warn_external(
                 "This figure was using a layout engine that is "
+                "incompatible with subplots_adjust and/or tight_layout; "