Well - the whole Lufthansa group has now eliminated cash refunds (even if it's in their T&C !) and resorts to vouchers (with a 50 CHF/USD/EUR inventive) or a refund payment "not before September".
Clearly illegal, at least from EU passenger rights regulations.
Of course, I understand the liquidity crunch - no lecture needed here. But the question is: why should we as passengers participate in their trouble, if before we weren't participating in the annual profits ?

Looking out further: either the airline goes under and then better do the chargeback now, as your M&B account won't be of much use anymore.
Or it will be bailed out by the Greek state or the EU, and then in the best case you have a voucher that you can use or not - in the worst case, they use the bailout to get rid of most liabilities (chapter 11 style) and with that your voucher and your M&B account.