Per the lancer core rules players should be able to see the whole battlefield including enemies. Sensors is the max range for tech actions.
I recommend using the less fog module if you want to have an indication of line of sight.
FoundryVTT module that reveals tokens within the sensor range of a mech in the Lancer system. Optionally requires libWrapper.
Paste the following url into the install module dialog in Foundry VTT: https://github.com/BoltsJ/sensor-sight/releases/latest/download/module.json