There's so many things that could happen that the fact that there's no clear cut answer may in itself be the message. The author could simply be trying to get people to think about mortality in general.
There's the troll ending: "You didn't think he'd actually die did you? It's just a title lololololol"
The twist ending where he dies in a societal sense or in some other way dies some metaphorical 'death' that leaves him breathing.
The sudden ending where suddenly a falling piano and the point of the manga was to live each day to the fullest as you never know what's going to happen.
The bitter end where suddenly disease and the point is to show that people who end up on life support were once just like you, so take care of yourself.
The dark ending where he gets depressed and the message is that even your seemingly normal friend can have shit going on.
Then there's the hyper troll mega twist deluxe with a lemon on top and he dies but is reincarnated into another world and it's all a prologue to the authors new isekai.
Or the reader abuse ending "The only reason it got to 100 chapters was because of your support, so YOU killed him!"