On 6 May 2021, Londoners will vote in their sixth mayoral election. I’ve polled London Grindr users twice before, for the 2017 and 2019 general elections. (I’ve also polled Scotland 6 times – on Scottish independence, Brexit, the 2015, 2017, and 2019 general elections, and the 2019 European election; the United States twice – on…