Not quite any radio protocol. Matter is an IPv6 based protocol that works over Ethernet, WiFi, and Thread. It does not natively support Z-wave or Zigbee. It is designed to replace both of them. Some vendors, like Hue and Aqara, are adding Matter Bridge support to their hubs to allow their Zigbee networks to work with Matter.
IIRC, Bluetooth is only used by Matter as part of the device discovery and onboarding process.
Yes, it is designed by a large consortium of major players (Apple, Google, Amazon, plus many others.) As such, they have incorporated improved security and encryption.
Matter has the concept of Controllers, which can share devices with other Controllers, thereby allowing all Devices to be used across multiple Matter platforms (e.g. Apple Home, Google Home, Amazon Alexa, Home Assistant, etc…) simultaneously. There are no device specific drivers required, as interoperability is part of the specification. This means no more vendor specific integrations for all of the major voice assistants.
To support Matter over Thread. one needs at least one Thread Border router. Multiple Thread Border routers may be implemented on a single Thread Mesh network. This has the promise of improved reliability and robustness. Thread is a much better network for low power battery powered devices compared to WiFi. Eventually, there is supposed to be a bunch of contact, motion, leak, and other sensors all based on Thread. Some Apple HomePods, some Amazon Echos, and some Google Home devices already have Thread radios onboard.
Time will tell if Matter is a success…or just one more standard.
Here is a more detailed explanation about Matter