Amazon improves the smart home device compatibility of its eero 6 and eero 6 Pro routers with its newest software update (eeroOS 6.4). The update adds Thread support, which allows it to work with other Thread-supported smart home devices, even from different manufacturers.
For example, Apple's HomeKit and the HomePod mini supports Thread, which means the compact smart speaker can automatically communicate with eero 6 routers and other Thread-enabled accessories. You don't need to configure anything from your end.
According to 9to5Mac, Thread support is disabled by default, so you'll need to head to Settings > Wireless > Thread to get it to work. You will also need to reboot your network twice.