from 2016, till 2019 i visited Doha almost four times!
simply, while i had long transit i applied for city tour on their counter near gate A4
its not guarantee to get Qatar transit visa, its individual decision by the qatar immigration!
so if you have a transit for like 6 hours, you can try your luck for city tour, it will cost you around $20.
the city tour bus will take you on a tour bus around some highlights of the city including: Katara, The Pearl, Museum of Islamic Art and around 45 minutes free walk in Souq Waqif. in total the city tour will last for around 2.5 - 3 hours.
kindly check their official website for time table, remember you cant book online, its first show first serve:
if you book early with qatar airways, you can apply for transit visa online, by making a layover in doha! only if both your flights are with qatar airways.
for up to date information kindly check their official website: