Amazon’s not-yet-released Eero Pro 6e and Eero 6+ WiFi 6e routers will turn 4th gen Echo and Echo Dot devices into wifi extenders through a feature called “eero Built-in device”. 4th gen Echo and Echo Dot (and Echo Dot Clock) devices are currently the only “eero Built-in device” compatible devices. They will be able to “Provide even more wifi for the devices in your connected home” i.e. act as wifi extenders.
There are some minor downsides to using an Echo as a wifi extender. First it will consume more power. Also you must link your Amazon account to your Eero account. Finally Echo devices will not be able to participate in Alexa Home Theater system.