The headlights are pretty good from stock. With 3 positions: DLR (peripheral lights), Low beam (middle lights) and high beam (top light). The bottom light is always on. Low beam is switched on automatically when the sensor on the dashboard detects darkness, or manually if DLR is turned off in the menus (this may be useful in fog for example).
There is no obvious spots to put additional lights, and so far not a lot of installs have been published. I’ve seen a very long video with lights installed on the lower tube supporting the front end (but warning the clearance with the forks is very tight) and this very extensive install report on Facebook.
Denali now offers 790 Adv specific mounts, also mounted on the lower tube, but with an additional leg to stabilise it.
KTM added lights to its catalog: P/N 63514910033, 487€. Those are PIAA lights, made by Valeo for KTM. It’s unclear where they mount from this picture, but they come with quite an assortment of hardware.