O que aconteceu com Darth Maul?

Sim, bem, mais ou menos. Star Wars: Darth Maul - Filho de Dathomir é considerado totalmente canônico. Ele explica os eventos que estão ocorrendo no final das Guerras Clônicas, mas ainda não há nada descrevendo o que acontece depois das Guerras Clônicas.

Por Wookieepedia:

Son of Dathomir is an adaptation of unproduced scripts from Star Wars: The Clone Wars, which would have been part of the television show's sixth season had the series not been cancelled in 2013. Although thirteen episodes from the sixth season were released as "The Lost Missions" on March 7, 2014, the episodes that Son of Dathomir were based on were not completed and therefore not released as actual episodes. The story is part of The Clone Wars Legacy line.

Eles fornecem uma sinopse geral:

The series is set during the Clone Wars, and is a continuation of Darth Maul's story from the show. The rogue Sith Lord, who was revealed to have survived the events of Star Wars: Episode I The Phantom Menace in the episode "Witches of the Mist," has been captured by his former master, Darth Sidious, following the events of the episode "The Lawless." Sidious uses Maul in an attempt to draw Mother Talzin, Maul's mother and the leader of the Nightsisters, out of hiding so she can be destroyed, as Sidious considers her a potential threat to the eventual Sith domination of the galaxy. Maul confronts the Confederacy of Independent Systems and captures Count Dooku and General Grievous in pursuit of vengeance against his old master, while the Galactic Republic and Jedi Order become involved in the hopes that they can defeat Maul, Dooku, and Grievous—and, in doing so, end the Clone Wars.

Agora sabemos uma quantidade razoável das atividades de Maul no final das Guerras Clônicas, e além:

• Como phantom42 observa em sua resposta , a série de quadrinhos canônica Darth Maul: Son de Dathomir vê Maul escapar da custódia de Sidious (onde nós o vimos pela última vez no show de The Clone Wars), capturando Dookan e Grievous e os trazendo para Dathomir em uma tentativa de atrair e matar Sidious Isso (inevitavelmente) falha, e Maul foge com o que resta de sua fiel Olhar da Morte

• Da próxima vez que o virmos, Ahsoka o localizou em Mandalore. Ela leva alguns clones para caçá-lo, mas a operação é interrompida pela Ordem 66; Maul subsequentemente escapa:

  She should have been at the Temple. She should have been with Anakin. She should have helped. Instead, she'd been on Mandalore, almost entirely alone, surrounded by clones and confusion and blaster fire. Maul had escaped, of course. She'd had the opportunity to kill him, but had chosen to save Rex instead. She didn’t regret that, couldn’t regret it, but the mischief and worse that Maul might wreak in a galaxy with no Jedi to protect it gnawed at her.

  ^Ahsoka

• Em algum momento ele evidentemente se colocou no radar de Vader, já que o Inquisidor conhecido como Oitavo Irmão era enviado por ele para tirá-lo:

  Dispatched by Darth Vader, he was sent to Malachor to attempt to find and capture Maul

• Como revelado no episódio de "Rebels of the Apprentice", ele conseguiu chegar a Malachor; ele alega que seu navio caiu, deixando-o lá:

  Ezra: You live here? Alone in the dark?

  Maul: Not by choice. My ship crashed; I'm trapped, marooned, I've had to scrounge and scrape to survive.

  ^{Star Wars: Rebels Season 2 Episode 20: "Twilight of the Apprentice Part 1"}

  No entanto, considerando seu objetivo final, isso parece ser uma meia verdade:

  Maul: [Ezra] is activating the temple; or, more precisely, this battlestation, which I shall use to exact my revenge on all my enemies!
  
  ^{Star Wars: Rebels Season 2 Episode 21: "Twilight of the Apprentice Part 2"}

  Ele escapa no final do episódio.

• Ao longo de dois episódios (não sequenciais) da terceira temporada de “Rebels”, “Holocrons of Fate” e “Visions and Voices”, Maul descobre que seu inimigo odiado Wan Kenobi sobreviveu à Ordem 66 e está se escondendo em planeta deserto com dois sóis .

• Isso vem à tona na temporada 3 episódio "Twin Suns", em que Maul rastreia Obi-Wan para baixo em Tatooine.

  They duel, and Maul is killed