Also there is nothing in the logs.

After I uncommented in httpd.conf the line

ErrorLog /var/log/httpd/mailman-web_error.log

I've got more info about the issue.

It was permission error:

ValueError: Unable to configure handler 'file': [Errno 13] Permission denied: '/var/log/mailman-web/mailman-web.log'

After I corrected permissions for log file mentioned I can access Postorius and Hyperkitty. Everything looks working, I will test in more details later.

Thanks!

Danil