See also ongoing work by @aisk in #113620. Perhaps you could coordinate your efforts?

@erlend-aasland, do you want to review these two PRs?
If you merge one I'll be happy to resolve the conflicts on the other one.

@erlend-aasland, do you want to review these two PRs? If you merge one I'll be happy to resolve the conflicts on the other one.

Sure, I'll get to it later today.

Done. I'll update this after #113620 is merged.

I think this is ready for review. Sorry for mistakenly wiping out old commits (from web).

Actual diff with a1ade06:

--- Modules/_ctypes/_ctypes.c
+++ Modules/_ctypes/_ctypes.c
@@ -128,13 +128,6 @@
-static PyTypeObject UnionType_Type;
 static PyTypeObject Union_Type;
 static PyTypeObject Struct_Type;
 static PyTypeObject Simple_Type;
 
 ctypes_state global_state = {
     .PyCStgDict_Type = &PyCStgDict_Type,
-    .PyCStructType_Type = &PyCStructType_Type,
-    .UnionType_Type = &UnionType_Type,
-    .PyCPointerType_Type = &PyCPointerType_Type,
-    .PyCArrayType_Type = &PyCArrayType_Type,
-    .PyCSimpleType_Type = &PyCSimpleType_Type,
-    .PyCFuncPtrType_Type = &PyCFuncPtrType_Type,

Thanks, Victor!

I merged this change which is a good start for futher work. I closed my similar duplicated (less complete) PR.