Thought I'd share the data point I have.

My flight departing 13 Apr was cancelled on 07 Apr.

Called in on 07 Apr, went through the tedious process of listening to the agent convince me to take an open ticket. (To be fair to him, he said all calls are recorded and they must offer this option first)

Got a refund confirmation on 04 May (advising that it may take 4-6weeks), and then money back on 08 May. (Which is the normal processing time for SQ from official refund confirmation, in all my years of dealing with cancellations.)

So far in this Covid crisis:
The best performer was BA with a refund time of 8 days. Despite them removing the option to refund via manage my booking. (I called to request)
The poorest performer is LH who is owing for 60+ days now, and the agents have a real attitude, totally gives the vibes of we'll refund you when we feel like it. So naturally I filed a chargeback.

I think 1 month is fair play in times like this. LH group is just disgusting. So post-COVID, definitely not flying on LH, OS, LX, SN.