Well the books George Lucas had read and approved as cannon, last as I remember were very few - however all the books I've described we're still Still Star Wars Books granted legitimacy by Lucas publishing and Co. However George himself had not approved of them as cannon best I remember.
If Luke ever actually Dies in the Films it will be a clone or some fakery Luke is using to confuse the enemy I'm almost certain. In the Books and Comics Force Yoda and Force Kenobi and Force Vader are actually off fighting a War on the other side and Luke, who can at that point exist on both sides can't find them. It's so bad that he find's out the Force versions he has been talking to are actually a Copy of the aberrations created by Dark Side A.I. Simulation Technology, no joke - suddenly these Hero's he's been talking to from the Light Side of the Force even in The Last Jedi/Rise Of Skywalker are turned by this realization - but he allows them to remain so because he realizes yes the Dark Side were using these to Spy - it relayed to a base he basically already destroyed, and they were programmed to be exact copies of his friends. He does however eventually go and dismantle them.
Meanwhile, the real Force Yoda/Kenobi/Vader - he can't find. They are off in some wild war involving a different type of "Force" which the Force has sent Midichlorian to fight and investigate.
Books like "The New Jedi Order" which touch on these things we're published by the original Star Wars Publisher, of which there were over 600 when I looked 20 years ago published in the same vein. None of which
George Lucas would consider cannon personally, but really - some of these Books, officially published by Del Ray (Lucas Star Wars Book Publishing) were so good Lucas himself should be envious! Especially the ones about how amazing Luke Actually is - and Spoiler, in the books as cannon Luke Becomes Midichlorian Luke without dying, he is that well liked by the Light side and he himself agrees to do it.
But I can see them pulling from the books to explain away all types of things, like Luke can be anywhere on a Time Line now - or can send copies of himself, just as powerful as he is created by the Force to carry out tasks and missions. And he has allowed it to look like he has died before to confuse the enemy. When They say Luke is the greatest Jedi to ever Exist he really is! In the books Death can not touch him, he is one with the force, and capable of things fans of the movie wouldn't think had they not heard about some of it!