Bolt works at all times of day or night, yes. Very similar to Uber (except you always have to pay cash, there is no ability for card payments). But at least you get a price quoted up front, and there are plenty of ATMs in the Arrivals hall that accept foreign cards. Bolt to the medina gates would be around 15-20 Dinars (USD5-USD6.50). Rip-off white taxi in front of the airport will try and charge you in Euros. I have had them quote me EUR30 for a journey into town before, which is equivalent to 100 Dinars (so 5 x the Bolt price). Absolutely to be avoided!