Can I apply for a DTV in Vietnam through any consulate regardless of my location?

They are really finicky in Vietnam as to showing proof of your current location so once you do that and it satisfies them I don't see why you can't travel around a bit but just be ready to be called in for an interview.

The one where you are

In addition to the arrival stamp, you need to submit at least a hotel booking to prove your location. So you need to apply to the embassy that serves the location you are showing as proof. They sometimes ask for more info like a selfie with the hotel's name or a boarding pass or a screenshot of your google maps.

As for finding out which place falls under which embassy's jurisdiction, as soon as you choose Vietnam in the system, you will see a pop up window with the names of city and places (in red) which fall under which embassy. Da Nang for e.g, falls under HCMC jurisdiction.

I believe you have to apply from where you are. I've seen posts here for Da Nang where people have used either HCMC or Hanoi. I'm in Hanoi now and submitted the application via and agent on 14 July at around 5 pm. On Wednesday (16 July) late afternoon they requested additional documents. I was told by the agent this morning that it is in the "pre-approval stage". But I've seen plenty of posts here indicating that Hanoi is as fast as 3 to 5 business days. Hope this helps.

You should apply thru the consulate relating to the city you are in at time of application. It is ok to travel within the country post application

You apply through the consulate that serves the location you are in at the time of application