The Tully–Fisher (TF) relation links a spiral galaxy’s rotational velocity to its luminosity, providing a relative distance indicator whose zero-point must be calibrated with independent absolute distances before it can yield H0 (Tully & Fisher 1977; McGaugh 2012). In ΛCDM, TF- and baryonic TF–based H0 estimates depend sensitively on how rotation widths are measured, how inclination, internal extinction, stellar mass-to-light ratios, and selection effects are modeled, and on which calibrators are used, so the fact that TF-derived H0 sometimes sits between Cepheid/TRGB and CMB values exposes a complex web of potential rotation and selection biases that the minimal model struggles to disentangle cleanly (Teerikorpi 1997; Boubel et al. 2024).