The paper explores the potential impact of ultralight boson clouds surrounding black holes in binary systems on the orbital eccentricities and mass distributions of these systems, as observed by future gravitational-wave detectors. The authors find that for non-precessing binaries with chirp masses $\mathcal{M} \lesssim 10 M_{\odot}$ formed exclusively in isolation, larger-than-expected eccentricities ($e \gtrsim 10^{-2}$ at gravitational-wave frequencies $f_{\text{GW}} \simeq 10^{-2}$ Hz) could provide evidence for the existence of a new ultralight particle with a mass between $[0.5, 2.5] \times 10^{-12}$ eV. The predicted evolution of the eccentricity can also affect the in-band phase evolution and peak frequency, making these signatures unique and detectable with future detectors like LISA, mid-band, and Deci-hertz observatories. The study considers the dynamics of these systems, including the effects of Landau-Zener resonances and ionization, and provides analytical and numerical results to support these findings.The paper explores the potential impact of ultralight boson clouds surrounding black holes in binary systems on the orbital eccentricities and mass distributions of these systems, as observed by future gravitational-wave detectors. The authors find that for non-precessing binaries with chirp masses $\mathcal{M} \lesssim 10 M_{\odot}$ formed exclusively in isolation, larger-than-expected eccentricities ($e \gtrsim 10^{-2}$ at gravitational-wave frequencies $f_{\text{GW}} \simeq 10^{-2}$ Hz) could provide evidence for the existence of a new ultralight particle with a mass between $[0.5, 2.5] \times 10^{-12}$ eV. The predicted evolution of the eccentricity can also affect the in-band phase evolution and peak frequency, making these signatures unique and detectable with future detectors like LISA, mid-band, and Deci-hertz observatories. The study considers the dynamics of these systems, including the effects of Landau-Zener resonances and ionization, and provides analytical and numerical results to support these findings.