#  update-crypto-policies --show
DEFAULT

# cat /root/.ssh/config 
Host 10.73.224.33
  KexAlgorithms            +diffie-hellman-group14-sha1
  MACs                     +hmac-sha1
  HostKeyAlgorithms        +ssh-rsa
  PubkeyAcceptedKeyTypes   +ssh-rsa
  PubkeyAcceptedAlgorithms +ssh-rsa
  
# cat /root/openssl-sha1.cnf 
.include /etc/ssl/openssl.cnf
[openssl_init]
alg_section = evp_properties
[evp_properties]
rh-allow-sha1-signatures = yes

# export OPENSSL_CONF=/root/openssl-sha1.cnf

# virt-v2v -ic xen+ssh://root@10.73.224.33 xen-hvm-rhel7.8-x86_64 -ip /home/esxpwd 
[   0.2] Setting up the source: -i libvirt -ic xen+ssh://root@10.73.224.33 xen-hvm-rhel7.8-x86_64
root@10.73.224.33's password: 
[   4.1] Opening the source
nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]
nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]
nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]
nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]
nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]

nbdkit: ssh[1]: error: failed to connect to remote host: 10.73.224.33: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group18-sha512,diffie-hellman-group16-sha512,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256]
virt-v2v: error: libguestfs error: could not create appliance through 
libvirt.

Try running qemu directly without libvirt using this environment variable:
export LIBGUESTFS_BACKEND=direct

Original error from libvirt: internal error: process exited while 
connecting to monitor: 2024-05-22T06:22:49.225199Z qemu-kvm: -blockdev 
{"driver":"nbd","server":\{"type":"unix","path":"/tmp/v2v.RJkTO8/in0"},"node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap","cache":\{"direct":false,"no-flush":true}}: 
Requested export not available [code=1 int1=-1]

If reporting bugs, run virt-v2v with debugging enabled and include the 
complete output:

  virt-v2v -v -x [...]

# rpm -q  virt-v2v nbdkit libnbd guestfs-tools libguestfs libvirt-libs qemu-img

virt-v2v-2.5.4-1.el9.x86_64
nbdkit-1.38.0-1.el9.x86_64
libnbd-1.20.0-1.el9.x86_64
guestfs-tools-1.51.6-4.el9.x86_64
libguestfs-1.50.1-9.el9.x86_64
libvirt-libs-10.3.0-1.el9.x86_64
qemu-img-9.0.0-2.el9.x86_64

# export OPENSSL_CONF=/root/openssl-sha1.cnf


#  virt-v2v -ic xen+ssh://root@10.73.224.33 xen-hvm-rhel7.8-x86_64 -ip /home/esxpwd -o null
[   0.2] Setting up the source: -i libvirt -ic xen+ssh://root@10.73.224.33 xen-hvm-rhel7.8-x86_64
[   1.9] Opening the source
[   7.6] Inspecting the source
[  22.2] Checking for sufficient free disk space in the guest
[  22.2] Converting Red Hat Enterprise Linux Server 7.8 Beta (Maipo) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 138.1] Mapping filesystem data to avoid copying unused and blank areas
[ 139.4] Closing the overlay
[ 139.7] Assigning disks to buses
[ 139.7] Checking if the guest needs BIOS or UEFI to boot
[ 139.7] Setting up the destination: -o null
[ 141.1] Copying disk 1/1
█ 100% [****************************************]
[ 259.3] Creating output metadata
[ 259.3] Finishing off