According to Official Guinness Records,
The fastest time to type the alphabet on a touchscreen mobile phone is 5.78 seconds, and was achieved by Rachel Musiker (USA) in Austin, Texas, USA, on 8 October 2018.This record was achieved at the 2018 PRSA (Public Relations Society of America) Conference.
For a complete list of 2018 records, please visit 2018 Guinness Records in United States.