Check out Onju. You can buy the PCB from pcbway or there are some other options coming: https://www.crowdsupply.com/onju/onju-voice
homeassistant
Home Assistant is open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts. Perfect to run on a Raspberry Pi or a local server. Available for free at home-assistant.io
Can always build to your own spec: https://www.espressif.com/en/products/devkits/esp-audio-devkits
I saw something that might be using that Korvu board, the S3-BOX. Unfortunately, $50 and out of stock as far as I could find.
I simply use an USB conference speaker/microphone plus the Assist Microphone add-on. (in my case this one from Microsoft, it works great with my RasPi.)
I actually prefer that over the Echo or other embedded devices, as it is able to pick up my voice from further away and the output audio quality is much better. (My use case is something similar to commercial proprietary systems like from Amazon/Google.)
The M5Stack Echo I use on my night stand with push to talk for quick actions, for that it is enough.