Both work — nothing on MarbleMap requires the deal to cross a border; sourcing inside one country runs through exactly the same flow.
When you open a demand you set Delivery country and Delivery point (city / port) yourself, and nothing stops you from choosing your own country. A delivery from Türkiye to Türkiye is a perfectly valid demand. In the detailed wizard, listing only your own country under Acceptable supplier countries keeps the quotes domestic; leave it empty and offers may come from anywhere. (That narrowing field requires a Pro plan.)
None of the export-specific fields are mandatory: Incoterm and GTIP / HS Code are optional and can stay blank on a domestic demand. You can set Currency to your local one — TRY is among the 12 supported currencies.
Everything else stays the same: suppliers quote sealed-bid, you compare every offer on a single screen, and no commission is taken on the sale.
Also asked as: Can I use this for domestic sourcing? · Is exporting required? · Can I buy inside my own country? · Can I open a demand for a local delivery?