Cython 3.1.0 is in RC phase already, so we can expect a final release sooner than later. As #1559 shows, zeroconf currently doesn't work with it and I wasn't able to find any tracking issue for the issues.

I have been trying to fix it myself but I'm afraid it's above my pay grade. From what I gather, Cython 3.1 got better at type annotations in .py files, and all the issues I've hit were somehow related to type annotations.

I've filed #1574 to fix one case of low-hanging fruit.

Another issue I've noticed is the type mismatch in DNSRecord.ttl:

Other signature mismatches I couldn't grasp. It is possible that they are actually a bug in Cython, but I don't really know Cython, so I'd appreciate if someone with better understanding of it checked, and possibly reported a bug upstream.

FWICS I can reproduce the same error with the following minimal reproducer:

.pxd:

cdef void foo(object x);

.py:

def foo(x: int) -> None:
    ...

but I don't know how int is supposed to be mapped here.