There is no single drop-in replacement, because mono- and diglycerides perform several jobs at once: emulsification, crumb softening, and fat stabilization. The closest plant-based functional relatives are lecithins (E322), derived from soybeans or sunflower seeds, which manufacturers use for similar emulsifying purposes. Some producers substitute other plant-derived emulsifiers, or simply use plant-sourced E471 itself, which is fully vegan even though it carries the same name on the label.
For consumers, the practical alternative is product selection rather than ingredient substitution. Certified vegan versions of bread, margarine, and ice cream either use plant-derived mono- and diglycerides or avoid the additive entirely. In home cooking, the additive is simply unnecessary: homemade bread, nut butters, and baked goods hold together without industrial emulsifiers, and lecithin granules or aquafaba can cover many common emulsifying tasks. When a specific packaged product matters, contacting the manufacturer remains the only way to verify the source of the E471 it contains.