“…Indeed, we have a good lead on a potential anisotropy, namely a strong candidate direction, which can be tested by any emerging cosmological probe [42], provided data quality is sufficient. Arguably, one of the most exciting prospects are gravitational waves (GWs) [43], since one can bypass the distance ladder on the assumption that General Relativity is correct and there is no shortage of promising forecasts and timelines for GW determinations of H 0 [44,45,46,47,48,49,50,51,52,53,54]. These forecasts of course assume an FLRW Universe.…”