Each account has a currency
Transactions inherit their account's currency. Home can show balances grouped by currency. Spndy does not convert between currencies or apply exchange rates.
Display preference is not conversion
Profile → App settings lets you choose a preferred currency. Saving that preference does not change existing account or transaction currencies or convert amounts.
Correct an account's currency
Open an account from Home and choose its edit action. Review the currency correction carefully. Correcting a label is not a foreign-exchange transaction; the balance is not converted.
Unconverted aggregates
Budgets, reports and household views can show unconverted aggregates without a reliable single currency. Do not treat a sum of mixed currencies as one spendable currency. Use individual account records and currency-specific views to understand the amounts.