2021+ Alexa models can perform voice processing locally. This is configured via Device Settings in the Alexa app. Speech recognition accuracy is slightly degraded for opt-in to local processing, https://www.slashgear.com/amazon-skips-the-cloud-with-local-...
> Amazon is switching on local voice recognition processing, promising users of some of its latest Echo smart speakers and smart displays that they can have their Alexa commands avoid the cloud completely... taps into the retail giant's homegrown AZ1 Neural Edge chipset.. followed Google, Apple, and others in creating its own custom silicon. While the AZ1 may not have been able to power the whole Alexa experience, it was focused instead on specific voice recognition features.