The D’Alembert solution of the wave motion equation is an important basic formula in linear partial differential theory. The study of the D’Alembert wave is worthy of deep consideration in nonlinear partial differential systems. In this paper, we construct a (2+1)-dimensional extended Boiti–Leon–Manna–Pempinelli (eBLMP) equation which fails to pass the Painlevé property. The D’Alembert-type wave of the eBLMP equation is still obtained by introducing one arbitrary function of the traveling-wave variable. The multi-solitary wave which should satisfy the velocity resonance condition is obtained by solving the Hirota bilinear form of the eBLMP equation. The dynamics of the three-soliton molecule, the three-kink soliton molecule, the soliton molecule bound by an asymmetry soliton and a one-soliton, and the interaction between the half periodic wave and a kink soliton molecule from the eBLMP equation are investigated by selecting appropriate parameters.