only 2x SDDCs show up under "registered SDDCs" even though the Org has more than 5 SDDCs.

Only the SDDCs which were in the READY state at the time of adding the org, are added to the list.
You can try adding the org once again. You will have to use FACTORY RESET option to flush the existing data.

Hi Ashish, all the 5x SDDCs are in a READY state. I've used the factory reset option to flush the existing data but still seeing the same issue, only the first 2x SDDCs appear.

This is interesting. I downloaded the same OVA from here and tested on my org. All my SDDCs were listed as expected.
I also checked the source code and did not find anything that filters out SDDCs, except the READY state.

1. Can you try with another org / token?
2. Also check if the missing SDDCs are zero cloud SDDCs. We do not support those yet.

If the above pointers don't help, we can schedule a debugging session sometime.

Seems to be working on another Org! I've noticed the Sync Policies capabilities are only for onprem to SDDC, are there any plans to enable SDDC to SDDC DFW sync? Finally, does the source support NSX-V?

This version does support SDDC to SDDC DFW sync.

We do not support NSX-V as of now. If there is a requirement, we can add the support in upcoming versions. Are there any customers looking for policies migration from nsx-v to VMC?

A message suggesting only onprem as a source when trying SDDC to SDDC DFW sync. I have a few customers interested in nsx-v to VMC.

We will take a look at both of these in the upcoming version.