Yes the issue is that you can generally only rebook +/- three days into the window of the route operating again. They don’t seem to have waived this.
I think you can be sure that LH will cancel these flights for a very very long time indeed. In which case, just leave the booking as is and rebook without the limitations of the booking classes when they return to a normalish schedule.
The refund will always be an option and I’m sure your credit card will be able to sort you out if LH go bust in the meantime.