There are 7 Diary Pages, which are just white pages you mostly see near main missions. They will display an icon over them when you're looking at them if you have not collected it.
https://mapgenie.io/far-cry-6/maps/pagan-controlI used this to find the collectibles. You can click the stuff you don't want to see (like chests), to take them off the map and make it a little clearer!