Is it permissible to assist someone in paying off a usurious debt, and is there any suspicion of unlawfulness (haram) in that?

It is permissible to help a debtor pay off their usurious debt if they have repented to Allah Almighty. If they show remorse and repentance, there is no harm in collecting money to help them. Otherwise, do not assist them, lest you become accomplices in their persistence in committing this abomination. It is permissible to give Zakat to someone who has taken out a usurious loan if they are repentant. If they are not repentant, then giving it to others is more appropriate. The same applies, a fortiori, to money other than Zakat.