https://github.com/sethmlarson/socksio/pull/61

--- socksio-1.0.0/pyproject.toml.orig
+++ socksio-1.0.0/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=2,<3"]
+requires = ["flit_core >=2"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.metadata]