Crown events are starting to trickle in.
on the 13th you get to do a crown event with Rajang, Yian garuga, and Nargacouga. Rajang is not needed for the achievement.
Also Yian garuga and Scarred Yian garuga are separate crowns. Scarred is just the tempered version of YG.
If you're crown hunting and not wanting to save scum 80 fights in a row, the current wisdom is to just focus in on the elder dragons and Scarred Yian garuga.
Since yian garuga is one of the secret monsters like Brute Tigrex, Gold Rath, and Silver Rath, more than likely all of those guys will be getting crown events.
Also the reward types dictate crown chance
2 purple rewards are no crown
3 and above purple rewards all have a crown chance
Any quest with all silver or silver and bronze is no crown
Any quest with more than 1 bronze is no crown
One exception is 1 bronze, 1 silver, and 1 gold which are are no crown
3-4 silver and 1 gold are crown chance
1 bronze and all gold are a crown chance
Any variation of a quest reward with 1 bronze and any make up of gold and silver together is a crown chance
You need the crowns of Lunestra and Original Deviljho for iceborne. Deviljho is easy on the PS4 since there's a high rank event with both. Lunestra can also get crown chances on High Rank quests and events. I got my Lunestra crowns from the arch tempered event and she's way easier to fight on high rank than at Master Rank since the one shot kills are given to more moves at MR.