Yes indeed, and if i were to add to the list, the Chakma language of NE India/CHT and their overall culture and traditions are very much similar to us.
Much like my state, Nepal is also a multi ethnic and multicultural country, and Nepali the lingua franca of the tribes.
There are half a million of Indian indigenous Gorkha in Assam, and unlike the Nepalis in other parts of NE, here they are mostly integrated with our greater society. It is virtually impossible to distinguish a Gorkha from an Assamese for an outsider. Inter community marriage amongst us is very common, and they have seamlessly adopted the use of Assamese over many generations whilst retaining the use of their mother tongue too.
Understanding the language is easy but speaking proficiency is hard, more so when the Gorkhas use Assamese here.
Fascinating to note that there's so much in common amongst us language wise, inspite of the ethnic divide.
I really should not break my vow of silence, but this is too close to the heart.
In linguistic terms, if we look at the whole family of descendants of Magadhi/Kamrupi Prakrit as an aggregate, one can see a convex lens-shaped distribution, with the central axis running south-west (roughly Medinipur) to north-east (around Dibrugarh?). There is a wing to the north-west, Maithil, beyond that Nepali, but others are outliers; perhaps due to personal weakness, I tend to see Chatgaiya as an outlier. Otherwise, if we trace the dialectal changes, any area in this space can understand the speech of the contiguous area(s). The Gorkha speaking Assamese is an exception; they have been there for generations, and are really well-integrated into Assamese society, and only their surnames (sometimes) give them away. It is very difficult to explain to an outsider the ethnic composition of the Assam Rifles, for that reason.
What the Dhakaya - those speaking the Dhaka dialect - don't always understand is the discomfort that they cause neighbouring dialect-speakers; without going into the bunfight going on in this thread, it is good enough to point to the supercilious attitude of the west Bengali, totally unable to understand our rude, country dialect, until a good, swift kick in the pants brings sudden and near-total comprehension (they still can't speak it). Bhanu Kaka (Bhanu Bandyopadhyaya, a Bengali comedian) made a lifetime living out of these differences.
This discomfort is one of the reasons for this thread.
Speaking entirely for myself, and with malice fully intended, it would be nice if the Sylhetis could be given their own country, even, on condition, strict condition, that they never, ever commit cultural homicide, and offer their version of Mughlai food to unsuspecting westerners. I think they are confused people, and I think some of them are creating an identity crisis where there is no room for one, but that's all right. No dog in that fight.