I felt it was worth clarifying the status of Host OS updates when using the openBalena ecosystem as there are a couple of conflicting posts which are being referenced when users ask about the feature.
As per the openBalena repository README (see here) the Host OS update feature is not currently supported, however I acknowledge that it is technically possible to update a current balenaOS device remotely. The reason that we do not support this is due to the fact that the process is being changed in the future for a more robust mechanism.
The new process, which is being worked on, will be consistent across balenaCloud/openBalena and follow more closely the application update model. It will be a far more controlled process leading to safer OS updates and less manual interventent. The plan is to allow these updates to be controlled like the application services are meaning pinning a device to an OS release, rolling back to previous releases etc, should be possible.