Installing on a fresh Debian 11.3 armhf fails.

[hanetzer]

The specific point of failure is when trying to ./manage.py migrate --noinput
fatal: [openwisp2.domain]: FAILED! => {"changed": false, "cmd":

(env) www-data@openwisp2:/opt/openwisp2$ ./manage.py migrate --noinput
Traceback (most recent call last):
  File "/opt/openwisp2/./manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/opt/openwisp2/env/lib/python3.9/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/opt/openwisp2/env/lib/python3.9/site-packages/django/core/management/__init__.py", line 377, in execute
    django.setup()
  File "/opt/openwisp2/env/lib/python3.9/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/opt/openwisp2/env/lib/python3.9/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/opt/openwisp2/env/lib/python3.9/site-packages/django/apps/config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 790, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/opt/openwisp2/env/lib/python3.9/site-packages/openwisp_controller/config/models.py", line 3, in <module>
    from .base.config import AbstractConfig
  File "/opt/openwisp2/env/lib/python3.9/site-packages/openwisp_controller/config/base/config.py", line 15, in <module>
    from .base import BaseConfig
  File "/opt/openwisp2/env/lib/python3.9/site-packages/openwisp_controller/config/base/base.py", line 12, in <module>
    from netjsonconfig.exceptions import ValidationError as SchemaError
  File "/opt/openwisp2/env/lib/python3.9/site-packages/netjsonconfig/__init__.py", line 5, in <module>
    from .backends.openvpn.openvpn import OpenVpn  # noqa
  File "/opt/openwisp2/env/lib/python3.9/site-packages/netjsonconfig/backends/openvpn/openvpn.py", line 5, in <module>
    from .renderer import OpenVpnRenderer
  File "/opt/openwisp2/env/lib/python3.9/site-packages/netjsonconfig/backends/openvpn/renderer.py", line 1, in <module>
    from ..base.renderer import BaseRenderer
  File "/opt/openwisp2/env/lib/python3.9/site-packages/netjsonconfig/backends/base/renderer.py", line 1, in <module>
    from jinja2 import Environment, PackageLoader
  File "/opt/openwisp2/env/lib/python3.9/site-packages/jinja2/__init__.py", line 12, in <module>
    from .environment import Environment
  File "/opt/openwisp2/env/lib/python3.9/site-packages/jinja2/environment.py", line 25, in <module>
    from .defaults import BLOCK_END_STRING
  File "/opt/openwisp2/env/lib/python3.9/site-packages/jinja2/defaults.py", line 3, in <module>
    from .filters import FILTERS as DEFAULT_FILTERS  # noqa: F401
  File "/opt/openwisp2/env/lib/python3.9/site-packages/jinja2/filters.py", line 13, in <module>
    from markupsafe import soft_unicode
ImportError: cannot import name 'soft_unicode' from 'markupsafe' (/opt/openwisp2/env/lib/python3.9/site-packages/markupsafe/__init__.py)

Seems its this issue coming to bite us.
pallets/markupsafe#284