How can I get a patch from a PR?

I looked at Creating patch from GitHub pull request (Example)
and when I tried this one https://patch-diff.githubusercontent.com/raw/python/cpython/pull/1982.patch
and ran

cpython on  main [$] via :snake: v3.11.0a6+
✦ ❯ git am --patch-format=mbox 1982.patch
Applying: bpo-30587: Adds signature checking for mock autospec object method calls
error: patch failed: Lib/unittest/mock.py:103
error: Lib/unittest/mock.py: patch does not apply
error: patch failed: Lib/unittest/test/testmock/testmock.py:1376
error: Lib/unittest/test/testmock/testmock.py: patch does not apply
Patch failed at 0001 bpo-30587: Adds signature checking for mock autospec object method calls

Is there ‘correct’ way to do this?
Or is it that a 3.8 patch is incompatible with the latest 3.11.0a6?

Correct, Git is telling you that the patch does not apply cleanly as the underlying source changed in the meantime. You might want to try git am -3 1982.patch (short for --3way), which will leave you with conflict markers in the files rather than just failing this way.

Yes that worked. I could see in VS code where the issue was and could simply accept/reject changes. Thanks.