@DaziStoNeD
Google Nest's standard recommendation for when customers are moving or selling their devices (https://support.google.com/googlenest/answer/11151047?hl=en#zippy=%2Cspeakers-and-displays) is to remove the device from the Google Home app (or Google Nest app) and then do a factory reset. If the first step (removing the device) is not done, you get a "connected to another account" error when trying to install the device and cannot proceed. They even say you should return the device for a refund if this happens (https://support.google.com/googlenest/answer/9249728?hl=en). (It seems Google Nest devices should not be sold until they are removed from the owner's Google account.)
Some customers have been able to contact Google Nest Support and, after providing the device's serial number, have Google Nest reset the device in some fashion so installation is possible, starting with this contact link:
https://support.google.com/googlenest/gethelp
