If you've played any of the previous Uncharted games, then you'll have a good idea of what's involved for the Platinum. Like the other titles in the series, you'll need to complete a Crushing mode playthrough, find numerous collectibles, fulfill some kill-related challenges, and unlock a few other miscellaneous trophies. A Chapter Select is available for mopping up what you're missing. Also, once the game is completed, a number of modifiers such as infinite ammo and weapon select are available, which makes a second playthrough on Crushing mode easier than on previous Uncharted installments.

Expect roughly 15-20 hours for the Platinum, depending on skills and how many playthroughs are performed.

Unlike many previous games in the Uncharted series, Crushing Mode is available from the start. So if you wish to avoid two playthroughs, and you're confident in your skills, you can get this out of the way from the very beginning.

However, be warned that playing on Crushing mode with make unlocking numerous trophies along the way quite challenging. Also, by playing and completing the game on any mode, you will unlock modifiers such as weapon select and infinite ammo, which would later make your Crushing mode playthrough much easier.

As you play, you'll want to be on the lookout for the 68 treasures you'll need to collect for the Collector Of Antiquities trophy. Check out the collectible locations guides and walkthroughs under our Links tab for help with these. You'll also need to find and unlock all 21 lockboxes for the Picks Or It Didn't Happen trophy, take a photo of all 28 photo opportunities for the Pics Or It Didn't Happen trophy, find all 11 Hoysala tokens for the Yas Queen trophy, listen to all 17 optional conversations for the Getting To Know You trophy. If you miss anything, don't fret. You can always use the Chapter Select after your first playthrough to collect whatever you still need. The only exception is related to the Yas Queen trophy, as some collectibles will be inaccessible until you've recovered all 11 Hoysala tokens.

Also, there are several kill-related trophies to work on, and some miscellaneous chapter-specific trophies which you can attempt to unlock during your first playthrough. Check out the Uncharted The Lost Legacy trophy guide links under our Links tab for more details. Again, if you miss them, you can always go back and use the Chapter Select.

There is one trophy which is technically missable. In order to unlock The Way Of The Warrior trophy, you'll need to reach the outskirts of Halebidu in Chapter 5 without using any firearms or explosives. This means you cannot use guns or explosives in the previous four chapters, up until you pass through the large doors into Chapter 5. This will be difficult to do if your first playthrough is on Crushing mode, but easy on Explorer. If you accidentally fire a weapon or throw a grenade, than quickly exit the game and reload to the last check point.

If you've completed the game on a difficult mode under Crushing, then your next step is to play through on Crushing mode. Remember, you can now use modifiers to help you. This is also a good chance to unlock any weapon kill-related trophies, or anything else you're still missing.

Once all that's finished, simply use the Chapter Select to mop up anything you're still missing. Check out the Uncharted The Lost Legacy trophy guide links under our Links tab to see what you still need, and their requirements.

Enjoy!

Here's a Walkthrough on IGN:
https://www.ign.com/wikis/uncharted-the-lost-legacy/Walkthrough

A text-based Walkthrough by dark52:
https://gamefaqs.gamespot.com/ps4/202464-uncharted-the-lost-legacy/faqs/75184

And Sehran Shaikh has a Walkthrough here:
https://www.gamepur.com/guide/27428-uncharted-lost-legacy-wiki.html

Here's a great Trophy Guide by Sellers:
https://www.playstationtrophies.org/game/uncharted-the-lost-legacy/guide/

And PowerPyx has a useful Trophy Guide here, with plenty of videos:
http://www.powerpyx.com/uncharted-the-lost-legacy-trophy-guide-roadmap/

And a useful Trophy Guide by MECHnation:
https://psnprofiles.com/guide/6375-uncharted-the-lost-legacy-trophy-guide

Primeraespada91 has a useful Trophy Guide here:
https://fextralife.com/uncharted-the-lost-legacy-trophy-guide-roadmap/

Here is a set of all-in-one Collectibles Guide videos by PowerPyx:
https://www.playstationtrophies.org/forum/uncharted-the-lost-legacy/314373-uncharted-lost-legacy-collectibles-guide.html

And a video demonstration of the Shadow Theater trophy by PowerPyx:
https://www.youtube.com/watch?v=Q3-MBhVVl6Y

Finally, here's a basic Trophy List:
https://www.truetrophies.com/game/Uncharted-The-Lost-Legacy/trophies?gamerid=124232