You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

sagemath-objects
10.4b3

This version was deleted from PyPI around 2025-05-04. Installing fails with:
$ pip3 install sagemath-objects==10.4b3 ERROR: Could not find a version that satisfies the requirement sagemath-objects==10.4b3