Is it Islamically permissible to record debts in US dollars and then repay them in Turkish Lira at the exchange rate at the time of repayment to avoid loss, knowing that purchasing goods in US dollars and selling them retail in Turkish Lira is the common practice due to the unavailability of small denominations of US dollars?

If the sale was made in Lebanese Lira, then it is impermissible to record the debt in its equivalent in US Dollars; the buyer is obligated to pay the agreed-upon price. Any excess money taken in this manner must be returned to its owners.

It is permissible to agree to pay the debt in a currency different from the currency of the debt on the day of payment, at its exchange rate on that day. If, during the contract session, the dollar price was agreed upon and the buyer consented, then there is no objection to that. If you both wish to pay in Lira upon maturity, it is permissible at the exchange rate of the day of payment, as long as you do not part ways while there is still something between you.