Yes, the missing person in Enola Holmes 2, Sarah Chapman, is real, and the movie is based on the person's true story.

Needless to say, the true story is slightly transformed to make the film more interesting. Although Enola Holmes and Sherlock Holmes are not real, and their extraordinary character is purely fictional, the story of Enola Holmes Season 2 is based on a true story. 

Sarah Chapman is a woman working at the Bryant & May match factory who went missing after theft allegations.

This workplace had young women as most of their workers, but many of them were dying of Typhus one by one. The culprit was not Typhus but Phosphorus, which was used to make the matches.

The papers Sarah stole contained the information and records of women who lost their lives due to this new element used in the factory. She intended to reveal this to the public and gain justice.

The real Sarah Chapman was born on 31 October 1862 and passed away on 27 November 1945. She was the leader of workers' strike that occurred in 1888 against the Bryant and May Match Factory.

She was also recognized as the pioneer of Gender equality and fairness at work. Her movement led 1400 girls to resign from work and the factory owners were forced to agree on their terms.

The real Sarah Chapman whose true story is portrayed in Enola Holmes Season 2.
Source : spitalfieldslife