One sourced entry per platform. Pick the one you already use to see exactly what its vendor documents about Matter and Thread.
Apple
What Apple's own published documentation states about Matter transports, Thread-enabled home hubs, and sharing accessories with other ecosystems.
What Google's developer and help documentation states about Matter transports, which Nest devices act as hubs and Thread border routers, and multi-admin.
Amazon
What Amazon's Alexa smart home developer documentation states about Matter over Wi-Fi and Thread, Echo Thread border routers, and Matter multi-admin.
Samsung
What Samsung's SmartThings support documentation states about Matter transports, which hubs carry a Thread border router, and sharing devices across platforms.
Open Home Foundation
What the Home Assistant Matter and Thread integration pages state about transports, the hardware a border router needs, and joining a device to several controllers.