It's safe to say, fans are still divided over how the most recent Star Wars movies evolved. Many believed Disney was scrubbing away the Expanded Universe, only for bits and pieces to be pulled back into play. However, they didn't think proper time was given for these arcs, especially Palpatine's rebirth, to be fleshed out.
After all, the Emperor was suddenly rushed into Star Wars: Episode IX - The Rise of Skywalker, mimicking the clone arc from the Expanded Universe. Instead, some felt this lore should have been mined to improve Mark Hamill's Luke Skywalker, rather than make him a bitter recluse who hated the Jedi Order. However, there's some solace to be gained from knowing Luke did have a version of his wife from these non-canon stories, reaffirming the Expanded Universe is living on spiritually in more ways than many know.
Star Wars Didn't Officially Use Mara Jade
When the sequel films revealed Luke had tried to rebuild the Jedi, many thought his wife, Mara Jade, would be brought in. She was a former Sith assassin like Darth Maul, who was meant to kill Luke, only to switch sides after her master, Palpatine, died and the Empire fell. They'd reform the Jedi, fight off terrorists and work hard to ensure the Sith never came back.
They even had a son, Ben, with Luke finding hope and light like never before. Sadly, Jacen Solo (Han and Leia's son) would fall prey to the dark side and murder Mara Jade. He felt she was a traitor to the Sith, so she had to go if he was to restart the sinister group. Such a direction could have gone a long way to making Luke a bit more digestible, with him and Mara Jade possibly working on a new Jedi sect, helping Rey unlock her future as a Chosen One.
Shadow of the Sith Has a Mara Jade Pastiche
Adam Christopher's 2022 novel, Shadow of the Sith, had someone quite similar to Mara Jade as Luke began investigating Ochi and clues that Palpatine's cult was around. This woman was Komat, a Sith disciple who was part of the Acolytes of the Beyond. They were tasked with gathering relics and shaping a path for Palpatine's rebirth, but Komat flipped on them when she realized they'd destroy the galaxy.
This book eventually had Luke and Lando recruiting her when her former colleague, Kiza, became possessed by a scary Sith Lord, Viceroy Exim Panshard. Komat ended up working with Luke to hunt down the warrior, leading to a brutal battle where Kiza and Exim both died. And make no mistake, Komat was quite formidable in the scrap, syncing up well with Luke. Even Lando noticed their chemistry, which nodded to Han and Leia.
Eventually, Komat went back to her secluded planet of Polaar, offering Luke a place if he needed. However, he was focused on Ben Solo and his young charges, which felt like a missed opportunity as he could have invited her to stay with him just over a decade after Star Wars: Episode VI - Return of the Jedi. He was already rejigging the religion, after all, and seeing as Komat didn't want her former cult rising up, this did indeed set up a Mara Jade arc. Ultimately, the potential was never realized as Luke would die years later battling Kylo Ren, leaving fans wondering if maybe in the time in between, there are secret stories and dates that Lucasfilm has yet to tell on paper.