Technically if you are a tourist you cannot fly which I did not know till later.
However, I went to the terace of my hotel and flew from there. Was able to reach Blue Mosque but barely Ayasofya.
That being said fly at your own risk. If you do just use common sense, and take off from somewhere not that crowded and take off fast. Because of city noise, nobody would hear the drone more than a few seconds if you fly up fast enough
I usually stick to the rules and if I knew you cannot fly in major cities or you had to be a Turkish national, I probably would have not flown.
At the end it was worth it! Beautiful country. Supposedly you can obtain a permit so you can try reaching an embassy for one.