If you run the command sudo do-release-upgrade -d through SSH then use a GNU Screen, because the upgrade process will turn off SSH -> close the default port and open a new one (it will inform you of this new port), so:
If you run the command sudo do-release-upgrade -d through SSH then use a GNU Screen, because the upgrade process will turn off SSH -> close the default port and open a new one (it will inform you of this new port), so: