Having added a Matter over Thread device to a hub or hub group, it is possible to use multi-admin to add the same device to another SmartThings hub in the same Location as if there are two separate devices.
This was how I had things set up. Three V3 hubs were in a hub group with automatic hub backup disabled (I don’t have a lot of confidence in it) so that there were three TBRs on the same thread network. This is the only way I know of achieving this with SmartThings hubs at the moment. My assumption is that if the primary TBR becomes unavailable one of the other hubs will be promoted to the primary TBR.
The V3 hubs are all powered by matter over thread devices and these were made available as separate devices on my beta hub, which is on the same Location but outside the hub group, which would allow me to manually or automatically restore power to a hub if it got turned off by accident. Or so I thought.
A little while ago I found all my Zigbee Buttons on my hub group weren’t functioning (no idea why) so I thought I’d take the opportunity to test things and powered off the primary hub. However when I went to turn it back on using the separate ST device on the beta hub it was offline. This was somewhat unexpected.
I am not saying I had a particularly sensible setup but I rather thought it should have worked.
I think that third party access via Google was still working as expected (I was not daft enough to not also have the devices available outside of SmartThings). I need to test that further though.