Changes:

• Enum now has an __index__ method on Python <3.8 too. #3700
• Local internals are now cleared after finalizing the interpreter. #3744

Bug fixes:

• Better support for Python 3.11 alphas. #3694
• PYBIND11_TYPE_CASTER now uses fully qualified symbols, so it can be used outside of pybind11::detail. #3758
• Some fixes for PyPy 3.9. #3768
• Fixed a potential memleak in PyPy in get_type_override. #3774
• Fix usage of VISIBILITY_INLINES_HIDDEN. #3721

Build system improvements:

• Uses sysconfig module to determine installation locations on Python >= 3.10, instead of distutils which has been deprecated. #3764
• Support Catch 2.13.5+ (supporting GLIBC 2.34+). #3679
• Fix test failures with numpy 1.22 by ignoring whitespace when comparing str() of dtypes. #3682

Backend and tidying up:

• clang-tidy: added readability-qualified-auto, readability-braces-around-statements, cppcoreguidelines-prefer-member-initializer, clang-analyzer-optin.performance.Padding, cppcoreguidelines-pro-type-static-cast-downcast, and readability-inconsistent-declaration-parameter-name. #3702, #3699, #3716, #3709
• clang-format was added to the pre-commit actions, and the entire code base automatically reformatted (after several iterations preparing for this leap). #3713