Measurements of $CP$ violation are a core part of the LHCb physics program to over constrain the CKM matrix and to understand the differences between matter and antimatter. The world's most precise measurement of $A_{CP}$ in $B^- \to D^- D^0$ decays is presented alongside the first measurement of $A_{CP}$ in the $B^- \to D_s^- D^0$ channel. Results from $B_{(s)}^0 \to \overline{D}^0 KK$ decays are also shown, including the first observation of the $B_s^0 \to \overline{D}^0 KK$ channel and inspections of the Dalitz plots.