Quantitative vanishing-regularization limits for degenerate cross-diffusion with changing boundary strata

We study a vanishing-regularization limit for a degenerate cross-diffusion system on the simplex when the active boundary stratum of a smooth reference solution may change in space and time. The mobility $M(u)=\operatorname{diag}u-u\otimes u$ loses rank when a component vanishes, so a fixed relative