  A theory of electron-phonon mediated superconductivity requires the knowledge
of full phonon spectrum to calculate superconducting transition temperature,
T$_c$. However, there is no experimental technique which can measure phonon
spectrum in highly-compressed near-room-temperature (NRT) superconductors to
date. In this paper we propose to advance McMillan's approach (1968 Phys Rev
167 331) which utilizes the Debye temperature, T$_{\theta}$ (an integrated
parameter of full phonon spectrum), that we deduced by the fit of
experimentally measured temperature-dependent resistance data, R(T), to
Bloch-Gruneisen equation for highly-compressed black phosphorous, boron, GeAs,
SiH$_4$, H$_x$S, D$_y$S, LaH$_x$ and LaD$_y$. By utilizing relations between
T$_c$, Debye temperature and electron-phonon coupling strength constant,
$\lambda_{e-ph}$ it is possible to affirm/disprove the electron-phonon
mechanism in given superconductors. We show that computed $\lambda_{e-ph}$ for
highly-compressed black phosphorous, boron, GeAs, SiH$_4$ and for one sample of
LaH$_{10}$ are in a good agreement with $\lambda_{e-ph}$ values deduced from
experimental data. It is also found remarkable constancy of Debye temperature
in H$_3$S at different ageing stages. We also show that if phonon spectra of
two isotopic counterparts have similar shape then within electron-phonon
phenomenology these materials should obey the relation of
T$_{c,1}$/T$_{c,2}$=T$_{\theta,1}$/T$_{\theta,2}$ (where 1 and 2 designate
isotopes). We report that these ratios for H$_3$S-D$_3$S predicted by
electron-phonon phenomenology are largely different from ratios deduced from
experiment. This alludes that NRT superconductivity in H3S-D3S system is
originated from more than one mechanism, where the electron-phonon coupling
lifts T$_c$ in H$_3$S vs D$_3$S, but primary origin for NRT background of in
both H$_3$S and D$_3$S remains to be discovered.
