I went through the validation process for focal-yoga UCA successfully, here it's the evidence:

$ juju ssh magnum/0 "apt policy python3-magnum"
python3-magnum:
  Installed: 14.1.0-0ubuntu1~cloud0
  Candidate: 14.1.0-0ubuntu1~cloud0
  Version table:
 *** 14.1.0-0ubuntu1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu focal-proposed/yoga/main amd64 Packages
        100 /var/lib/dpkg/status
     10.0.0-0ubuntu0.20.04.2 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages
     10.0.0~b3~git2020041013.01629398-0ubuntu1 500
        500 http://nova.clouds.archive.ubuntu.com/ubuntu focal/universe amd64 Packages
Connection to 10.5.3.92 closed.


$ tox -e func-target -- keystone_v3_smoke_focal_magnum:focal-yoga
-magnum
func-target: commands[0] /mnt/git/charmed-openstack-tester/tests/distro-regression> functest-run-suite --keep-model --bundle keystone_v3_smoke_focal_magnum:focal-yoga-magnum
2023-05-21 22:52:35 [INFO] Deploying bundle '/mnt/git/charmed-openstack-tester/tests/distro-regression/tests/bundles/focal-yoga-magnum.yaml' on to 'zaza-829e38068354' model
2023-05-21 22:52:36 [INFO] Rendered template '<Template 'local-charm-overlay.yaml.j2'>' to file '/tmp/tmp5tlhpydd/local-charm-overlay.yaml'
2023-05-21 22:52:37 [INFO] Rendered template '<Template 'focal-yoga-magnum.yaml.j2'>' to file '/tmp/tmp5tlhpydd/focal-yoga-magnum.yaml'
2023-05-21 22:52:37 [INFO] Deploying overlay '/tmp/tmp5tlhpydd/local-charm-overlay.yaml' on to 'zaza-829e38068354' model
2023-05-21 22:52:37 [INFO] Deploying overlay '/tmp/tmp5tlhpydd/focal-yoga-magnum.yaml' on to 'zaza-829e38068354' model
...
['tempest', 'run', '--workspace', 'zaza-829e38068354', '--config', '/home/ubuntu/.tempest/zaza-829e38068354/etc/tempest.conf', '--smoke', '--exclude-regex', '^(octavia_tempest_plugin|manila_tempest_t
ests|designate_tempest_plugin)\\..*', '--include-list', '/tmp/tmp50yypvo8/include.cfg', '--exclude-list', '/tmp/tmp50yypvo8/exclude.cfg']
...
======
Totals
======
Ran: 120 tests in 1721.5379 sec.
 - Passed: 111
 - Skipped: 9
 - Expected Fail: 0
 - Unexpected Success: 0
 - Failed: 0
Sum of execute time for each test: 1020.3695 sec.

==============
Worker Balance
==============
 - Worker 0 (120 tests) => 0:28:41.537929
2023-05-22 00:08:55 [INFO] Finished testing zaza-829e38068354
2023-05-22 00:08:55 [INFO] Events:
  Configure zaza.openstack.charm_tests.glance.setup.add_cirros_alt_image:
    Start: 1684712137.652861
    Finish: 1684712145.7448723
    Elapsed Time: 8.092011213302612
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.glance.setup.add_cirros_image:
    Start: 1684712128.697704
    Finish: 1684712137.6524868
    Elapsed Time: 8.954782724380493
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.glance.setup.add_lts_image:
    Start: 1684711806.5355585
    Finish: 1684711882.862383
    Elapsed Time: 76.326824426651
    PCT Of Run Time: 2
  Configure zaza.openstack.charm_tests.glance_simplestreams_sync.setup.sync_images:
    Start: 1684711512.5890179
    Finish: 1684711806.534925
    Elapsed Time: 293.9459071159363
    PCT Of Run Time: 7
  Configure zaza.openstack.charm_tests.heat.setup.domain_setup:
    Start: 1684712145.7452025
    Finish: 1684712172.4183974
    Elapsed Time: 26.673194885253906
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.keystone.setup.add_demo_user:
    Start: 1684712081.9137044
    Finish: 1684712123.2428997
    Elapsed Time: 41.32919526100159
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.keystone.setup.add_tempest_roles:
    Start: 1684712123.243409
    Finish: 1684712128.6973789
    Elapsed Time: 5.453969955444336
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.magnum.setup.add_image:
    Start: 1684712192.5729165
    Finish: 1684712349.6628528
    Elapsed Time: 157.0899362564087
    PCT Of Run Time: 4
  Configure zaza.openstack.charm_tests.magnum.setup.domain_setup:
    Start: 1684712172.4187593
    Finish: 1684712192.5726492
    Elapsed Time: 20.153889894485474
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.neutron.setup.basic_overcloud_network:
    Start: 1684711882.8631084
    Finish: 1684712058.9941769
    Elapsed Time: 176.13106846809387
    PCT Of Run Time: 4
  Configure zaza.openstack.charm_tests.nova.setup.create_flavors:
    Start: 1684712058.9950483
    Finish: 1684712074.8118029
    Elapsed Time: 15.816754579544067
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.nova.setup.manage_ssh_key:
    Start: 1684712074.8122847
    Finish: 1684712081.9132032
    Elapsed Time: 7.100918531417847
    PCT Of Run Time: 1
  Configure zaza.openstack.charm_tests.vault.setup.auto_initialize:
    Start: 1684711093.4112463
    Finish: 1684711512.5884757
    Elapsed Time: 419.17722940444946
    PCT Of Run Time: 10
  Deploy Bundle:
    Start: 1684709555.5139968
    Finish: 1684709724.8847094
    Elapsed Time: 169.37071251869202
    PCT Of Run Time: 4
  Prepare Environment:
    Start: 1684709545.3206308
    Finish: 1684709555.5114338
    Elapsed Time: 10.190803050994873
    PCT Of Run Time: 1
  Test zaza.openstack.charm_tests.tempest.tests.TempestTestWithKeystoneV3:
    Start: 1684712349.6656942
    Finish: 1684714135.8123631
    Elapsed Time: 1786.1466689109802
    PCT Of Run Time: 39
  Wait for Deployment:
    Start: 1684709724.8848343
    Finish: 1684711093.4052787
    Elapsed Time: 1368.520444393158
    PCT Of Run Time: 30
Metadata: {}

  func-target: OK (4600.54=setup[0.39]+cmd[4600.15] seconds)
  congratulations :) (4601.38 seconds)