little do the ..., what is this

ALL the sentences are correct.
It depends on the meanings you want to bring out.

(1)Little do the citizens know this kind of technology well nowadays.
Correct. "Know..well" means " quite familiar with.."
But the meaning is different from the other 3 sentences,
It means the citizens know the technology, but not very familiar with it.
The rest mean the citizens do not know the technology.

(2)Little do the citizens know this kind of technology nowadays.
Correct, the same as the correct sentence of number 3.
Just changing the position of the adverb.
for example:
Little do the citizens nowadays know this kind of technology.

(3)Nowadays, little do the citizens know this kind of technology.
*Nowadays is an adverb, no need to put a comma at its back.
Correct sentence:
Nowadays little do the citizens know this kind of technology.

(4)Little do the citizens know this kind of technology.
Correct, it means:
The citizens do not know this kind of technology.

Little do = do not
for example:
Little does she know what trouble she is in
= She does not know what trouble she is in.

A lot does she eat after swimming.
She eats a lot after swimming.

Hope my explanation is enough to make you understand.
Thank you.

中文
做公民現今知道這种技術。