I've reassigned this bug to libvirt. Longer description is below, but in short if you just install virt-v2v on a new RHEL 9.4 install and try a conversion, it fails with the weird error:

virt-v2v: error: exception: libvirt: VIR_ERR_OPERATION_UNSUPPORTED: 
VIR_FROM_REMOTE: Operation not supported: Cannot use direct socket mode if 
no URI is set

The solution (I don't know how you'd guess this) is to do:

# systemctl start virtqemud-ro.socket

If the socket is required for libvirt to work then it should be started when libvirt is installed, or else the error message should explain exactly how to resolve the problem.

What were you trying to do that didn't work?
The error info is not clear when execute virt-v2v on a newly installed rhel 9.4 server

Please provide the package NVR for which bug is seen:
virt-v2v-2.3.4-5.el9.x86_64
qemu-img-8.1.0-4.el9.x86_64
libvirt-libs-9.5.0-7.el9_3.x86_64

How reproducible:
100%

Steps to reproduce
1. Prepare a newly installed rhel 9.4 server and install virt-v2v

2. Convert a guest from VMware by virt-v2v

1. virt-v2v -ic vpx://administrator%40vsphere.local@10.73.213.182/data/10.73.212.38/?no_verify=1 -it vddk -io vddk-libdir=/home/vddk8.0.1 -io vddk-thumbprint=85:C2:91:55:86:E5:BE:08:60:96:64:8D:54:6E:3F:39:A5:F5:1F:19 -ip /home/passwd esx7.0-rhel7.9-x86_64 -v -x
   virt-v2v: virt-v2v 2.3.4rhel=9,release=5.el9 (x86_64)
   libvirt version: 9.5.0
   libguestfs: trace: set_verbose true
   libguestfs: trace: set_verbose = 0
   libguestfs: trace: get_backend
   libguestfs: trace: get_backend = "libvirt"
   virt-v2v: error: exception: libvirt: VIR_ERR_OPERATION_UNSUPPORTED:
   VIR_FROM_REMOTE: Operation not supported: Cannot use direct socket mode if
   no URI is set
   rm -rf – '/tmp/v2v.wXEAdo'
   libguestfs: trace: close
   libguestfs: closing guestfs handle 0x5606632b4540 (state 0)

3. Start virtqemud-ro.socket manually

1. systemctl start virtqemud-ro.socket

4. Convert a guest from VMware by virt-v2v again

1. virt-v2v -ic vpx://administrator%40vsphere.local@10.73.213.182/data/10.73.212.38/?no_verify=1 -it vddk -io vddk-libdir=/home/vddk8.0.1 -io vddk-thumbprint=85:C2:91:55:86:E5:BE:08:60:96:64:8D:54:6E:3F:39:A5:F5:1F:19 -ip /home/passwd esx7.0-rhel7.9-x86_64
   [ 0.0] Setting up the source: -i libvirt -ic vpx://administrator%40vsphere.local@10.73.213.182/data/10.73.212.38/?no_verify=1 -it vddk esx7.0-rhel7.9-x86_64
   [ 1.7] Opening the source
   [ 19.3] Inspecting the source
   [ 25.5] Checking for sufficient free disk space in the guest
   [ 25.5] Converting Red Hat Enterprise Linux Server 7.9 (Maipo) to run on KVM
   ......

Expected results
Should prompt a clear error to tell user which service or socket should be started

Actual results
The error isn't clear