This update is working for me in local testing (using about 60 ports that depend on setuptools-scm).

This breaks for python3.9 and python3.10 at build time because of the following requirement in the setuptool-scm 9.2.0 pyproject.toml:

'tomli<=2.0.2; python_version < "3.11"'

The ports tree currently has tomli 2.2.1

The following patch removes this restriction and setuptools-scm builds and installs successfully for python3.9 and python3.10 and tomli 2.2.1, and it functions correctly (returns the correct version information), and a large number of dependent ports are building (although I did not run a full coverage local exp-run):

--- pyproject.toml.orig 2025-08-04 09:14:50 UTC
+++ pyproject.toml
@@ -4,7 +4,7 @@
 build-backend = "_own_version_helper:build_meta"
 requires = [
   "setuptools>=61",
-  'tomli<=2.0.2; python_version < "3.11"',
+  'tomli; python_version < "3.11"',
 ]
 backend-path = [
   ".",

The addition of that restriction upstream appears to be wrong and is in question:

https://github.com/pypa/setuptools-scm/issues/1090