Python 3.10 introduced asyncio changes that broke compatibility with earlier 3.x releases. I don't have the details at hand, but as I recall, some code that supported caller-supplied event loops not only broke, but could no longer be made compatible with both old 3.x and new 3.x python versions (unless separate code paths were maintained).
This was frustrating, because I don't expect point-releases to break the standard library, let alone require a code fork to maintain cross-distro compatibility. It was disappointing, because I had never encountered such breakage from python while Guido was still in charge.
I had the same experience. I was pretty annoyed to see that some server apps were unable to run after the upgrade because of some changes to the loop. "Why?", I was asking myself.
This was frustrating, because I don't expect point-releases to break the standard library, let alone require a code fork to maintain cross-distro compatibility. It was disappointing, because I had never encountered such breakage from python while Guido was still in charge.