The only similarity to the vCenter BZ is how the broken ref in the inventory results in a 500. Aside from that, this bug is completely different. A significant question is - Why is the profile ref in the vNIC empty?
All the networks in this RHV have a vNIC profile, except for one called "internal" that doesn't have one. The error in the migration UI: "Error loading VMs 500: Internal server error" If there are RHV components, other than vNIC profile, that might be empty and may fail the RHV inventory the same way should also be handled.
Fixed by API resolving the vNIC profile only when not blank.
Verified 2.1.0-44 iib:96817 successfully UI migrated from RHV with Network without vnic profile.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (Migration Toolkit for Virtualization 2.1.0), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHEA-2021:3278