diff --git a/doc/api/next_api_changes/removals/30067-OG.rst b/doc/api/next_api_changes/removals/30067-OG.rst
new file mode 100644
index 000000000000..d70d2ed51714
--- /dev/null
+++ b/doc/api/next_api_changes/removals/30067-OG.rst
@@ -0,0 +1,23 @@
+``TransformNode.is_bbox``
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+... is removed. Instead check the object using ``isinstance(..., BboxBase)``.
+
+``rcsetup.interactive_bk``, ``rcsetup.non_interactive_bk`` and ``rcsetup.all_backends``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+... are removed and replaced by ``matplotlib.backends.backend_registry.list_builtin``
+with the following arguments
+
+- ``matplotlib.backends.BackendFilter.INTERACTIVE``
+- ``matplotlib.backends.BackendFilter.NON_INTERACTIVE``
+- ``None``
+
+``BboxTransformToMaxOnly``
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+... is removed. If you rely on this, please make a copy of old the code.
+
+*interval* parameter of ``TimerBase.start``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+The timer interval parameter can no longer be set while starting it. The interval can be specified instead in the timer constructor, or by setting the timer.interval attribute.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
index 2158990f578a..9f168f323b4c 100644
--- a/lib/matplotlib/backend_bases.py
+++ b/lib/matplotlib/backend_bases.py
@@ -1067,19 +1067,8 @@ def __del__(self):
         """Need to stop timer and possibly disconnect timer."""
         self._timer_stop()
 
-    @_api.delete_parameter("3.9", "interval", alternative="timer.interval")
-    def start(self, interval=None):
-        """
-        Start the timer object.
-
-        Parameters
-        ----------
-        interval : int, optional
-            Timer interval in milliseconds; overrides a previously set interval
-            if provided.
-        """
-        if interval is not None:
-            self.interval = interval
+    def start(self):
+        """Start the timer."""
         self._timer_start()
 
     def stop(self):
diff --git a/lib/matplotlib/backend_bases.pyi b/lib/matplotlib/backend_bases.pyi
index 2d7b283bb4b8..b637ee4b32f9 100644
--- a/lib/matplotlib/backend_bases.pyi
+++ b/lib/matplotlib/backend_bases.pyi
@@ -186,7 +186,7 @@ class TimerBase:
         callbacks: list[tuple[Callable, tuple, dict[str, Any]]] | None = ...,
     ) -> None: ...
     def __del__(self) -> None: ...
-    def start(self, interval: int | None = ...) -> None: ...
+    def start(self) -> None: ...
     def stop(self) -> None: ...
     @property
     def interval(self) -> int: ...
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
index ce29c5076100..02e3601ff4c2 100644
--- a/lib/matplotlib/rcsetup.py
+++ b/lib/matplotlib/rcsetup.py
@@ -24,7 +24,7 @@
 
 import matplotlib as mpl
 from matplotlib import _api, cbook
-from matplotlib.backends import BackendFilter, backend_registry
+from matplotlib.backends import backend_registry
 from matplotlib.cbook import ls_mapper
 from matplotlib.colors import Colormap, is_color_like
 from matplotlib._fontconfig_pattern import parse_fontconfig_pattern
@@ -34,32 +34,6 @@
 from cycler import Cycler, cycler as ccycler
 
 
-@_api.caching_module_getattr
-class __getattr__:
-    @_api.deprecated(
-        "3.9",
-        alternative="``matplotlib.backends.backend_registry.list_builtin"
-            "(matplotlib.backends.BackendFilter.INTERACTIVE)``")
-    @property
-    def interactive_bk(self):
-        return backend_registry.list_builtin(BackendFilter.INTERACTIVE)
-
-    @_api.deprecated(
-        "3.9",
-        alternative="``matplotlib.backends.backend_registry.list_builtin"
-            "(matplotlib.backends.BackendFilter.NON_INTERACTIVE)``")
-    @property
-    def non_interactive_bk(self):
-        return backend_registry.list_builtin(BackendFilter.NON_INTERACTIVE)
-
-    @_api.deprecated(
-        "3.9",
-        alternative="``matplotlib.backends.backend_registry.list_builtin()``")
-    @property
-    def all_backends(self):
-        return backend_registry.list_builtin()
-
-
 class ValidateInStrings:
     def __init__(self, key, valid, ignorecase=False, *,
                  _deprecated_since=None):
diff --git a/lib/matplotlib/rcsetup.pyi b/lib/matplotlib/rcsetup.pyi
index 79538511c0e4..eb1d7c9f3a33 100644
--- a/lib/matplotlib/rcsetup.pyi
+++ b/lib/matplotlib/rcsetup.pyi
@@ -4,9 +4,6 @@ from collections.abc import Callable, Iterable
 from typing import Any, Literal, TypeVar
 from matplotlib.typing import ColorType, LineStyleType, MarkEveryType
 
-interactive_bk: list[str]
-non_interactive_bk: list[str]
-all_backends: list[str]
 
 _T = TypeVar("_T")
 
diff --git a/lib/matplotlib/tests/test_backend_registry.py b/lib/matplotlib/tests/test_backend_registry.py
index 80c2ce4fc51a..2bd8e161bd6b 100644
--- a/lib/matplotlib/tests/test_backend_registry.py
+++ b/lib/matplotlib/tests/test_backend_registry.py
@@ -3,7 +3,6 @@
 
 import pytest
 
-import matplotlib as mpl
 from matplotlib.backends import BackendFilter, backend_registry
 
 
@@ -95,16 +94,6 @@ def test_backend_normalization(backend, normalized):
     assert backend_registry._backend_module_name(backend) == normalized
 
 
-def test_deprecated_rcsetup_attributes():
-    match = "was deprecated in Matplotlib 3.9"
-    with pytest.warns(mpl.MatplotlibDeprecationWarning, match=match):
-        mpl.rcsetup.interactive_bk
-    with pytest.warns(mpl.MatplotlibDeprecationWarning, match=match):
-        mpl.rcsetup.non_interactive_bk
-    with pytest.warns(mpl.MatplotlibDeprecationWarning, match=match):
-        mpl.rcsetup.all_backends
-
-
 def test_entry_points_inline():
     pytest.importorskip('matplotlib_inline')
     backends = backend_registry.list_all()
diff --git a/lib/matplotlib/transforms.py b/lib/matplotlib/transforms.py
index 2cca56f04457..7228f05bcf9e 100644
--- a/lib/matplotlib/transforms.py
+++ b/lib/matplotlib/transforms.py
@@ -98,7 +98,6 @@ class TransformNode:
     # Some metadata about the transform, used to determine whether an
     # invalidation is affine-only
     is_affine = False
-    is_bbox = _api.deprecated("3.9")(_api.classproperty(lambda cls: False))
 
     pass_through = False
     """
@@ -216,7 +215,6 @@ class BboxBase(TransformNode):
     and height, but these are not stored explicitly.
     """
 
-    is_bbox = _api.deprecated("3.9")(_api.classproperty(lambda cls: True))
     is_affine = True
 
     if DEBUG:
@@ -2627,27 +2625,6 @@ def get_matrix(self):
         return self._mtx
 
 
-@_api.deprecated("3.9")
-class BboxTransformToMaxOnly(BboxTransformTo):
-    """
-    `BboxTransformToMaxOnly` is a transformation that linearly transforms points from
-    the unit bounding box to a given `Bbox` with a fixed upper left of (0, 0).
-    """
-    def get_matrix(self):
-        # docstring inherited
-        if self._invalid:
-            xmax, ymax = self._boxout.max
-            if DEBUG and (xmax == 0 or ymax == 0):
-                raise ValueError("Transforming to a singular bounding box.")
-            self._mtx = np.array([[xmax,  0.0, 0.0],
-                                  [ 0.0, ymax, 0.0],
-                                  [ 0.0,  0.0, 1.0]],
-                                 float)
-            self._inverted = None
-            self._invalid = 0
-        return self._mtx
-
-
 class BboxTransformFrom(Affine2DBase):
     """
     `BboxTransformFrom` linearly transforms points from a given `Bbox` to the
diff --git a/lib/matplotlib/transforms.pyi b/lib/matplotlib/transforms.pyi
index 551487a11c60..07d299be297c 100644
--- a/lib/matplotlib/transforms.pyi
+++ b/lib/matplotlib/transforms.pyi
@@ -12,7 +12,6 @@ class TransformNode:
     INVALID_NON_AFFINE: int
     INVALID_AFFINE: int
     INVALID: int
-    is_bbox: bool
     # Implemented as a standard attr in base class, but functionally readonly and some subclasses implement as such
     @property
     def is_affine(self) -> bool: ...
@@ -24,7 +23,6 @@ class TransformNode:
     def frozen(self) -> TransformNode: ...
 
 class BboxBase(TransformNode):
-    is_bbox: bool
     is_affine: bool
     def frozen(self) -> Bbox: ...
     def __array__(self, *args, **kwargs): ...
@@ -295,8 +293,6 @@ class BboxTransform(Affine2DBase):
 class BboxTransformTo(Affine2DBase):
     def __init__(self, boxout: BboxBase, **kwargs) -> None: ...
 
-class BboxTransformToMaxOnly(BboxTransformTo): ...
-
 class BboxTransformFrom(Affine2DBase):
     def __init__(self, boxin: BboxBase, **kwargs) -> None: ...