Hi
frenchkiki and welcome to FlyerTalk!
Unfortunately, you won't be able to enter the international departures area with a domestic boarding pass;
However, there are two options that you could consider if you really want to visit a lounge
- If you are ( TK*S / Classic Plus or higher ) or *G, you could use the Turkish Airlines Domestic Lounge
- You could buy a dummy refundable ticket for the day after your arrival and clear transfer security at the international terminal with that boarding pass, after entering the lounge, you could cancel the ticket. If you are an IGAPass member or hold a Priority Pass, they shouldn't check your boarding pass at the IGA Lounge. You could do the same thing for the TK International Business Class Lounge if you purchase a TK J ticket or cancel.
Otherwise, there would be no access to a lounge in IST.
Also, depending on your travel date, the TK Arrival Lounge may open, however, we have no information about the opening date.