When portainer is installed on HassOS, this is considered as a not supported HA install. This could give some trouble updating in the future.
Since you are using proxmox, I would make 2 virtual machines.
One to install HA using the HassOS script you have. And the other to install docker and portainer on which you can install MSR as explained by toggledbits.
This way you can also use docker for all other sort of projects which are not related to HA without interfering with it.