In the UK they could technically be discharged through bankruptcy. But that takes a long time and ruins your life (you’ll be barred from a lot of carriers and lose basically everything).

In Qatar, it’s more complex. They use a weird mix of sharia and more western law. I’m not convinced these loans would be sharia compliant so maybe there is some wriggle room there? On the other hand suing the state airline in an absolute monarchy with no judicial independence may be difficult. I don’t think Qatar has a concept of bankruptcy (as all credit should be secured and limited against collateral). So they’re between a rock and a hard place.

Maybe they can flee and find a country (countries) that won’t enforce a Qatar civil judgement? But I think the west generally will so not sure where that leaves...