Sensitivity of CTA (red thick solid line) and HESS (red thick dashed line) telescopes for detection of the Galactic diffuse γ-ray emission. Green and yellow butterflies show the spectrum of the astrophysical neutrino signal detected in the cascade and through-going muon detection modes (Williams 2019). Light-to-dark grey solid lines show the flux levels of diffuse γ-ray emission from different parts of the sky measured by Fermi/LAT, as reported by Neronov & Semikoz (2020). Dashed lines of the same colour show high-energy power law extrapolation of the Fermi/LAT measurements. The Galactic Ridge signal (the darkest grey line) power law is modified by the effect of pair production on cosmic microwave background assuming a distance of 8 kpc. The dotted light red curve shows the sensitivity which could be achieved with a dedicated array of telescopes with a small and wide FoV.