Takeaway from python-lsp/python-lsp-ruff#61:

I managed to track it down. There's a type in lsprotocol.types, LSPAny, typed as Union[Any, None].
Looks like there's a regression in unstructuring this type, it used to be unstructured as the runtime type, and now is unstructured as Any.

Originally posted by @Tinche in python-lsp/python-lsp-ruff#61 (comment)

The issue is solved with cattrs>=23.2.2. Can we make the cattrs dependency more strict?