Ironically for a region that is the centre of mediaeval Bengal, Malda largely does not have modern Bangla as its mother tongue.

Rural Malda (and parts of Dinajpur/Murshidabad) dominated by Khotta or Eastern Maghi.

A sample (aptly enough it is a political adda on 2021 polls)

The name of the dialect (Khotta) also gives rise to a pejorative term for Biharis in Bengalis (in case you ever wondered about the etymology of this seemingly random slur).

Kolkata Hindustani borrows significantly from Maghi (along with obviously Bangla) btw due to migration.

Modern Maghi (tadhbhava for Magadhi, the language from which every eastern Indo-Aryan language descends) is closely related to Bangla but clearly not mutually intelligible.

Unfortunately inspite of this grand name, the language is not counted.

In Bihar/Jharkhand, it is subsumed within Hindi (to which it actually has very little relation). And in Bengal, Khotta speakers largely return (close cousin) Bengali as their mother tongue in the census.

If Maghi were counted, it would be a major language in India -- and hence the world -- in terms of numbers.

(That is true for almost all languages counted as "Hindi" under the census given the sheer population density of the Gangetic plain.)