Try different workaround #3

packer/ubuntuserver20.04.pkr.hcl

@@ -73,7 +73,7 @@ build {
     ansible_env_vars = [
       "ANSIBLE_CONFIG=ansible/ansible.cfg"
     ]
-    no_proxy         = "true"
+    use_proxy        = "false"
     extra_arguments  = [
       "-vvv"
     ]