Ticket immernoch nicht erstattet nach ueber 6 Monaten

I made a reservation for travel in December 2020 with Lufthansa via STA Travel at the binning of 2020. Mid 2020 STA Travel went into liquidation (with Deloitte as the administrator). As the booking (booking code VCEYVC) was already paid to Lufthansa by STA Travel, I was directed by Deloitte to request the refund due to COVID-19 directly from Lufthansa.
I have contacted Lufthansa first in October last year. Since then I had contacted Lufthansa Customer Relations 3 times without any resolution (just generic responses). I have called Lufthansa Australia and Germany numerous times without any resolution.
The estimated time for refunds by Lufthansa was advised to be within 6 weeks.
Lufthansa does not provide any contacts for special cases such as bookings through a travel agent who is in liquidation. They only provide the generic customer relation contact, which is a call centre contact without any ability to manage a complaint. Lufthansa does not offer any avenue for filing a complaint.
What can I do? Do you have any other contacts to Lufthansa to file a complaint?