Semileptonic $B$ decays from Belle and Belle II

This report summarizes recent measurements of the CKM matrix elements $\mathrm{\mid }{V}_{cb}\mathrm{\mid }$, $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$, and lepton-flavor universality tests in semileptonic B decays from the Belle and Belle~II experiments. The decay branching factions $R(D^{\ast })$ and $R(X)$ are measured with the Belle~II early dataset and the results are found to be consistent with the Standard Model predictions. From a simultaneous measurement of untagged $B^0\to {\pi }^{-}{\mathrm{\ell }}^{+}\nu$ and $B^{+}\to {\rho }^0{\mathrm{\ell }}^{+}\nu$, the $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$ value is determined incorporating external theoretical constraints on the decay form factors. The first measurement of the full angular coefficients for $B\to D^{\ast }\mathrm{\ell }\nu$ decays at Belle provides comprehensive information for determining the decay form factors and $\mathrm{\mid }{V}_{\mathrm{c}\mathrm{b}}\mathrm{\mid }$. This presentation also includes measurements of the ratios $\mathrm{\mid }{V}_{ub}{\mathrm{\mid }}^{\mathrm{e}\mathrm{x}\mathrm{c}\mathrm{l}}\mathrm{/}\mathrm{\mid }{V}_{ub}{\mathrm{\mid }}^{\mathrm{i}\mathrm{n}\mathrm{c}\mathrm{l}}$ and $\mathrm{\mid }{V}_{ub}{\mathrm{\mid }}^{\mathrm{i}\mathrm{n}\mathrm{c}\mathrm{l}}\mathrm{/}\mathrm{\mid }{V}_{cb}{\mathrm{\mid }}^{\mathrm{i}\mathrm{n}\mathrm{c}\mathrm{l}}$.