Radio emissions from an exoplanet can serve as an indicator for the presence of an advanced civilization.
Atmospherically present pollutants can be a strong indicator of industrial-like activity occurring on an exoplanet’s surface.
Gases associated with industrial activity can be produced naturally.
Natural nuclear reactors and artificial ground-based nuclear fission-related activities can affect a terrestrial planet’s atmospheric environment in analogous ways.
Anomalous, and/or excess, radiation emanating from an exoplanet’s surface can indicate the presence of an advanced civilization.
Natural materials readily interact with incident radiation on a cosmic scale.
If employed, sustainable technologies such as solar panels could be detection on an exoplanet’s surface.
Assuming the sustainability solution to the Fermi Paradox holds, a civilization should become more sustainable and therefore less detectable as it becomes more advanced.