This might simply have been because my Ubuntu version did not by default include installation of the python tool, and Microstack did not check that it was available.
I have since installed python manually, and the init stage now completes successfully:
js:~$ sudo microstack init --auto --control
[sudo] password for pjs:
2021-11-15 16:59:40,844 - microstack_init - INFO - Configuring clustering ...
2021-11-15 16:59:41,355 - microstack_init - INFO - Setting up as a control node.
2021-11-15 16:59:49,774 - microstack_init - INFO - Generating TLS Certificate and Key
2021-11-15 16:59:53,708 - microstack_init - INFO - Configuring networking ...
2021-11-15 17:00:16,440 - microstack_init - INFO - Opening horizon dashboard up to *
2021-11-15 17:00:19,064 - microstack_init - INFO - Waiting for RabbitMQ to start ...
Waiting for 192.168.0.14:5672
2021-11-15 17:00:20,891 - microstack_init - INFO - RabbitMQ started!
2021-11-15 17:00:20,892 - microstack_init - INFO - Configuring RabbitMQ ...
2021-11-15 17:00:23,363 - microstack_init - INFO - RabbitMQ Configured!
2021-11-15 17:00:23,504 - microstack_init - INFO - Waiting for MySQL server to start ...
Waiting for 192.168.0.14:3306
2021-11-15 17:00:25,497 - microstack_init - INFO - Mysql server started! Creating databases ...
2021-11-15 17:00:30,740 - microstack_init - INFO - Configuring Keystone Fernet Keys ...
2021-11-15 17:00:48,404 - microstack_init - INFO - Bootstrapping Keystone ...
2021-11-15 17:00:54,906 - microstack_init - INFO - Creating service project ...
2021-11-15 17:01:00,991 - microstack_init - INFO - Keystone configured!
2021-11-15 17:01:01,137 - microstack_init - INFO - Configuring the Placement service...
2021-11-15 17:01:13,021 - microstack_init - INFO - Running Placement DB migrations...
2021-11-15 17:01:21,137 - microstack_init - INFO - Configuring nova control plane services ...
2021-11-15 17:01:27,266 - microstack_init - INFO - Running Nova API DB migrations (this may take a lot of time)...
2021-11-15 17:01:57,686 - microstack_init - INFO - Running Nova DB migrations (this may take a lot of time)...
Waiting for 192.168.0.14:8774
2021-11-15 17:02:34,263 - microstack_init - INFO - Creating default flavors...
2021-11-15 17:03:09,258 - microstack_init - INFO - Configuring nova compute hypervisor ...
2021-11-15 17:03:09,259 - microstack_init - INFO - Checking virtualization extensions presence on the host
2021-11-15 17:03:09,330 - microstack_init - WARNING - /dev/kvm does not exist
2021-11-15 17:03:09,330 - microstack_init - WARNING - Hardware virtualization is not supported - software emulation will be used for Nova instances
2021-11-15 17:03:19,205 - microstack_init - INFO - Configuring the Spice HTML5 console service...
2021-11-15 17:03:21,894 - microstack_init - INFO - Configuring Neutron
Waiting for 192.168.0.14:9696
2021-11-15 17:04:28,618 - microstack_init - INFO - Configuring Glance ...
Waiting for 192.168.0.14:9292
2021-11-15 17:05:06,479 - microstack_init - INFO - Creating security group rules ...
2021-11-15 17:05:19,444 - microstack_init - INFO - Configuring the Cinder services...
2021-11-15 17:06:39,812 - microstack_init - INFO - Running Cinder DB migrations...
2021-11-15 17:07:02,273 - microstack_init - INFO - restarting libvirt and virtlogd ...
2021-11-15 17:07:18,732 - microstack_init - INFO - Complete. Marked microstack as initialized!
This might simply have been because my Ubuntu version did not by default include installation of the python tool, and Microstack did not check that it was available.
I have since installed python manually, and the init stage now completes successfully:
js:~$ sudo microstack init --auto --control
[sudo] password for pjs:
2021-11-15 16:59:40,844 - microstack_init - INFO - Configuring clustering ...
2021-11-15 16:59:41,355 - microstack_init - INFO - Setting up as a control node.
2021-11-15 16:59:49,774 - microstack_init - INFO - Generating TLS Certificate and Key
2021-11-15 16:59:53,708 - microstack_init - INFO - Configuring networking ...
2021-11-15 17:00:16,440 - microstack_init - INFO - Opening horizon dashboard up to *
2021-11-15 17:00:19,064 - microstack_init - INFO - Waiting for RabbitMQ to start ...
Waiting for 192.168.0.14:5672
2021-11-15 17:00:20,891 - microstack_init - INFO - RabbitMQ started!
2021-11-15 17:00:20,892 - microstack_init - INFO - Configuring RabbitMQ ...
2021-11-15 17:00:23,363 - microstack_init - INFO - RabbitMQ Configured!
2021-11-15 17:00:23,504 - microstack_init - INFO - Waiting for MySQL server to start ...
Waiting for 192.168.0.14:3306
2021-11-15 17:00:25,497 - microstack_init - INFO - Mysql server started! Creating databases ...
2021-11-15 17:00:30,740 - microstack_init - INFO - Configuring Keystone Fernet Keys ...
2021-11-15 17:00:48,404 - microstack_init - INFO - Bootstrapping Keystone ...
2021-11-15 17:00:54,906 - microstack_init - INFO - Creating service project ...
2021-11-15 17:01:00,991 - microstack_init - INFO - Keystone configured!
2021-11-15 17:01:01,137 - microstack_init - INFO - Configuring the Placement service...
2021-11-15 17:01:13,021 - microstack_init - INFO - Running Placement DB migrations...
2021-11-15 17:01:21,137 - microstack_init - INFO - Configuring nova control plane services ...
2021-11-15 17:01:27,266 - microstack_init - INFO - Running Nova API DB migrations (this may take a lot of time)...
2021-11-15 17:01:57,686 - microstack_init - INFO - Running Nova DB migrations (this may take a lot of time)...
Waiting for 192.168.0.14:8774
2021-11-15 17:02:34,263 - microstack_init - INFO - Creating default flavors...
2021-11-15 17:03:09,258 - microstack_init - INFO - Configuring nova compute hypervisor ...
2021-11-15 17:03:09,259 - microstack_init - INFO - Checking virtualization extensions presence on the host
2021-11-15 17:03:09,330 - microstack_init - WARNING - /dev/kvm does not exist
2021-11-15 17:03:09,330 - microstack_init - WARNING - Hardware virtualization is not supported - software emulation will be used for Nova instances
2021-11-15 17:03:19,205 - microstack_init - INFO - Configuring the Spice HTML5 console service...
2021-11-15 17:03:21,894 - microstack_init - INFO - Configuring Neutron
Waiting for 192.168.0.14:9696
2021-11-15 17:04:28,618 - microstack_init - INFO - Configuring Glance ...
Waiting for 192.168.0.14:9292
2021-11-15 17:05:06,479 - microstack_init - INFO - Creating security group rules ...
2021-11-15 17:05:19,444 - microstack_init - INFO - Configuring the Cinder services...
2021-11-15 17:06:39,812 - microstack_init - INFO - Running Cinder DB migrations...
2021-11-15 17:07:02,273 - microstack_init - INFO - restarting libvirt and virtlogd ...
2021-11-15 17:07:18,732 - microstack_init - INFO - Complete. Marked microstack as initialized!