I upgraded from 5.28 last night and ran into this same problem. I had an old version of haystack theme installed which was causing the problem (disabling the theme would bring the labels back).
You'll want to disable and uninstall haystack, delete the directory from your wp/uploads/civicrm/ext/ directory and then install the updated theme from here: https://...
WD civicrm: hook_civicrm_alter_drupal_entity_labels should be updated to [warning] pass an array of parameter names to CRM_Utils_Hook::invoke(). Array ( [civi.tag] => deprecated )
For this, i think you need to apply https://github.com/eileenmcnaughton/civicrm_entity/pull/238 patch in civicrm_entity module.