Your sole remedy from your TA, not LX, is a refund of the unused segments. That is fairly clear from Guidance issued by the EC which is non-binding as to Member States and perhaps less so as to Switzerland. Thus, if you cannot convince your TA to extend the fare rules (it is down to your TA, not LX), take the refund and purchase the cheapest ticket on any carrier in any class of service as the
#1 priority has to be repatriation.
You might also carefully review your travel interruption insurance (don't rely on what others tell you, but rather read the policy).
If you are out anything, you might consider pursuing the TA upon your return, but it is doubtful to be effective.