Are any countries accepting refuges from Russia that seek asylum? I know some Russians that are wholly against their Government's actions. I hope some provisions are being made to allow those who wish escape to do so...
I'm surprised no one has suggested, split future Upwork income. 50% goes to the debt and 50% goes to the developer. He's not working for free and they get their money back. It's the only solution that is equitable to all parties.
BTW - I have extensive experience in credit card processing. It is VERy DIFFICULT to reverse a chargeback. Upwork is at the mercy of Visa/MC/Amex, and the developer is at the mercy of Upwork. Upwork can choose to not use Visa/MC/Amex but they add enough value to accept the chargeback risk. The developer can choose to not use Upwork but they add enough value to accept the chargeback risk.
He can walk away from this, use a competing platform, and not pay a dime. Upwork has already paid back the $12k+ and are stuck, which is the primary reason why they should consider the 50/50 split of future income.