mailman3 - css files of hyperkitty placed in wrong directory

I have installed mailman3 and followed this instruction: https://lab.uberspace.de/guide_mailman-3/

My problem is, that css files for HyperKitty (and the login screen) are not available. If I'm on https://example.org/postorius/ everything looks good but on https://example.org/hyperkitty/ the main css file is not found.

In ~/mailman-suite/settings.py I set STATIC_ROOT = '/home/hmail/html/static/' and most of the files are placed there (and are available from the webserver), except some that are placed in ~/mailman-suite/home/hmail/html/static/ (which are not available from the webserver).

The HyperKitty website refers to /static/CACHE/css/hyperkitty.413473e09b83.css which is not placed in the right directory, but under /home/hmail/mailman-suite/home/hmil/html/static/CACHE/css/hyperkitty.413473e09b83.css

Any idea why or how I can fix this?

Installed versions:

• mailman3: 3.3.8
• HyperKitty: 1.3.7
• postorius: 1.3.8
• mailman-hyperkitty: 1.2.1
• whoosh: 2.7.4

I suspect that it is a path problem as /home/hmail/mailman-suite/home/hmil/html/static/ looks very similar to ~/mailman-suite/home/hmail/html/static/ - probably a lost "/"... But where can I adjust it?

Regards!
Stefan

You might need to add the following config into your settings.py (or settings_local.py) of Django:

CACHES = {
    'default': {
        'BACKEND': 'diskcache.DjangoCache',
        'LOCATION': '/home/hmail/html/static/CACHE',
    },
}

Docs: https://grantjenks.com/docs/diskcache/tutorial.html#djangocache