Download [Emulator]_Fire_Emblem_Engage_1.3.0_-_Force_60FPS.zip
Open Ryujinx, right-click on Fire Emblem Engage -> Open Atmosphere Mods Directory
Extract the exefs folder from the 60FPS zip there (it's inside the "Force 60FPS [v1.3.0]" folder)
And then it should work
Also, not sure if you have...