Hi Stefano.
Fusionhub does not support traditional HA/VRRP. As a virtual machine you would use the hypervisor capabilities to provide high availability and resilience for the VM itself and build out a HA core network infrastructure from your hypervisor to and from the internet to guarantee its availability.
When building public cloud hosted environments I always deploy Fusionhub in an active/active way as detailed above on different hosting platforms (ie AWS & AZURE). I find it hard to justify the expense of HA appliances in a single location, compared to the versatility and improved Disaster Recovery capabilities of a pair of appliances hosted in two seperate locations.
All Peplink devices support connecting to at least two remote peers via PepVPN/SpeedFusion for failover between two hub devices - whether they are deployed in active/active or active/failover.
In your case then where you have a single DC at a single location, I would suggest you run two seperate FH appliances, primary and secondary. All remote devices create two tunnels one to each FH. The Secondary FH appliance will have a higher metric set for the remote peers, the remote peers will also have higher metric set for the secondary FH profile. Then use OSPF between the Fusionhubs and the DC core router so that the primary is used until it is unavailable at which point OSPF updates send the traffic via the secondary.
Kindest,
Martin