I personally think the best way to handle it is to literally start or end the opening crawl with “General Leia Organa has passed away” And give a badass explanation on how she died fighting. To say how she will be forever Luminous, and be there with the Resistance in spirit. Through the force.
If they ACT like she is alive and is “Just on some other ship” and then that ship blows up, it will not make any sense and will feel cheap repeating what happened in Episode 8. It will feel so wrong and gross in my opinion. Either they talk about the funeral in the opening crawl, or the movie literally BEGINS with her funeral for a short period of time. With Poe speaking and taking on the mantle as the new general.
I cannot imagine it any other way. I pray they don’t just write her off as somewhere else and “fine” throughout the movie. If she were in the Star Wars Universe alive, we know she deserves to be seen!! And sadly, she cannot be.
I was talking with my brother about the same thing and made the same conclusion a few days ago. I would also like to make an animated movie to tell that story and released it on the official youtube channel (maybe on the May 4th) as a tribute.