  For a flat $\Lambda$CDM universe, the dipole of the luminosity distance can
be utilized to measure the Hubble parameter. It is here shown that this is not
the case in more general settings where curvature and cosmic backreaction is
permitted. This implies that a discordance between $H(z)$ measurements obtained
using such dipole luminosity distance data and "true"/actual $H(z)$ data
obtained from e.g. cosmic chronometers is a signal of curvature and/or cosmic
backreaction. \newline\indent By considering mock future gravitational wave
measurements of the Hubble parameter obtained through the dipole luminosity
distance, it is shown that already a $1\%$ curvature could in principle just
barely show up in the determination. However, for realistic mock data
generation using models with as much as 5 \% curvature, parameter estimates do
not yield reliable measures of inconsistency between the false $H(z)$
measurements and true measurements of $H(z)$. At the same time, cosmic
backreaction is hard to detect even if it makes up $10\%$ of the "energy
budget" in the current universe, even when considering a highly idealized
situation with low errors. The results concerning backreaction are based on
specific "scaling solutions" to the backreaction problem and the study shows
that the possibility of detecting a signal of backreaction through the dipole
of the luminosity distance depends strongly on the particular backreaction
model.
