It's absolutely wild. They've broken multicast and UDP for all applications that do not pay Apple money (like open source, community coded ones). Which means things like mouse/keyboard sharing applications like synergy/barrier/etc stopped working in many cases. But that's just the tip of the iceberg. And there's no way for a human to control this "multicast entitlement" on their own OS how they like it. The only way for applications on Sequoia to have multicast network access is for some commercial developer pay for it.
This is very not Unix. Careful out there "up"grading.