I found a solution:
C:\Users\<Username>\Documents\Respawn\Titanfall2\l
"setting.defaultres" "3840"
"setting.defaultresheight" "2160"
Works for me.
For 2024 people using the EA app on PC.
"setting.defaultres" "3840" <------- Delete 1920 and type 3840.
"setting.defaultresheight" "2160" <------ Delete 1080 and type 2160
Changing these settings in your game file still works. But I had a hard time locating the file. They have different locations than what people have mentioned here. It may have changed after Origin changed the name to EA.
After failing to locate it for quite some time I searched "titanfall2" in my file manager and "videoconfig" was the first result on the list.
For me it was: Local Disk (C: )/ Users/ My last name/ Documents/ Respawn/ Titanfall2/ Local/ Videoconfig
Edit: Airwolf-pro already said what i said. im just such a noob that i was looking for a file called "username" not realizing he meant MY USER NAME, which happened to be my last name. thats a name i never use as a username so im not sure where it came from or why that the file name. but airwolf pro's advice from 8 years ago is still exactly what i needed to do in 2024.
