To unlock the "SURVIVORS" trophy in Detroit: Become Human, you must make sure that all principal characters make it to the end of the game.
This is not just the three playable characters: On my first run through I did not unlock this trophy because characters directly tied to either Kara, Connor or Markus were killed before the end of the game. So make sure the following characters make it as well as the protagonists: Hank, Alice, Luther, North, Josh, Simon.
Here are some characters that can definitely die without repercussion, as the trophy still unlocked for me:
*** Spoiler - click to reveal ***-- Markus' owner Carl can die of a heart attack
-- Jerry can sacrifice himself for Kara, Alice and Luther in the final sequence at the Canadian border
-- The android from the very first chapter and the deviant android found by Connor at the broadcast tower can die; in fact it may be impossible to keep them alive (to be verified)
-- Zlatko can be killed while escaping his house
Below are some examples of where the protagonists' allies can get killed and some advice on how to avoid that, but there are hundreds of possibilities in this game. I will update with the ones that I find on repeated playthroughs.
As a general rule in a potentially lethal incident, avoid conflict and always choose to protect your allies however you can, in most cases you will only have to perform some QTEs anyway. The game leaves you with more ways out than you might think. Generally you should keep your allies loyal and friendly to avoid conflicts as well, and get the public on the side of the androids through peaceful non-violent protest. In other words, you should go for this trophy on your "Good ending" run; trophies that require violence or Connor's various deaths should be held back for a mop-up playthrough.
Markus' allies:*** Spoiler - click to reveal ***I am less certain that all three of Markus' Jericho allies - Simon, Josh and North - need to survive, but play it safe and make sure they do. Here are some known causes-of-death and how to avoid them, but also you should try your best to keep them all happy and loyal.
-- If the alarm is triggered during Markus' attempt to broadcast his message, armed forces will storm the broadcast room and Simon can get seriously wounded. If you get him to the roof but still end up leaving him behind, he can still survive. Just make sure Connor doesn't investigate the roof. He won't do so if Connor finds and is killed by the deviant in the kitchen (Connor keeps coming back so he can afford to die at this point).
-- If Jericho is stormed by the FBI and you choose to detonate the place, North may take a bullet on the way out. You should go back for her; successfully QTE her adversaries and you will make it out.
-- Choose PEACEFUL DEMONSTRATION in "Night of the Soul" to give everyone a chance of surviving. (I didn't make that clear enough, thanks Muljo for noticing!)
-- In the final chapter, when you march on the camps, stay as peaceful as possible and pass ALL QTEs. I didn't encounter any moments where the three allies could die by taking this route EXCEPT through failing QTEs; because North was Markus' lover in my playthrough she may sacrifice herself if you really mess up the final QTE behind the barricade.
Hank:*** Spoiler - click to reveal ***Generally you should keep Hank friendly towards Connor and just always choose to help him out if he gets into trouble.
-- When chasing down the android during "THE NEST", the android may end up knocking Hank off the side of a building. You have an opportunity to save Hank if you let the android get away.
-- Sparing the Tracis and the Chloe give significant boosts to Hank's friendliness towards you, as does successfully finding the deviant in "PARTNERS" and successfully interrogating it in "THE INTERROGATION". Additional brownie points with Hank if you intervene when Chris tries to force this android to move at the end of the chapter as well.
-- In the final chapter, if Connor has become deviant and travels to CyberLife to convert all the androids, a second Connor may threaten to kill Hank if you go through with it. Choose to save Hank rather than sacrifice him. Hank will attack the fake Connor, so make sure to attack the fake Connor as well when prompted. In my playthrough I had enough information on Hank's life (crucially the name of his son) for Hank to choose the right Connor to shoot.
Alice and Luther (credit to SolaceCreed for some Alice tips):*** Spoiler - click to reveal ***
-- Alice can be killed in Zlatko's house if you fail to reach her in time.
-- Luther can be killed while escaping Jericho when it is stormed by the FBI. Make sure to go back and grab him, taking out the guards in the process.
-- Play dead if the FBI catch up to you while escaping Jericho. If you end up in the Recycling Center you can still survive but it's much harder. Besides, you might as well aim to cross the border properly at the end for a different trophy.
-- While Kara is heading towards the bus in the Battle for Detroit chapter, you should come across Luther. Make sure to save him from the guard so that he joins your party. You'll also save Jerry at this point which is important for the next incident.
-- Alice will die if you miss the bus to Canada and don't take the river crossing.
-- All three can be killed if you take the river crossing to Canada. To play safe, make sure you get on the bus - you can do so by stealing the ticket that the young mother drops. When you get to the border, make sure to sacrifice Jerry rather than Luther (or yourself) if you must sacrifice anybody to get through security. Jerry doesn't count towards this trophy. You won't have to sacrifice anybody if Markus conducted a successful peaceful protest at the camp as the border guard will be sympathetic -- for those of you that want a "perfect" ending.