If you take the word of English Professor M Kieth Booker, then yes, Ash and - by extrapolation - all the later Androids are sentient.

From Ashs Wikipedia page
Emphasis mine

Like the alien organism itself, Ash (and indeed the sentient ship's computer, named "Mother") is presented as, in the words of M. Keith Booker, a "distinctive mode of intelligent existence that seems alien to our own", and is in fact (if one counts the dead pilot of the crashed spaceship) one of a number of sentient non-humans that humanity encounters in the film.

Also, Bishop is capable for emotion, from his Wikipedia page
Emphasis mine

Immediately after his activation, Bishop is quizzed by a technician named Dr. Sasaki to ensure he does not suffer from any potentially dangerous faults in his character programming. Sasaki releases Bishop into a room containing other similar androids, although she privately voices her concern that he may be flawed, possessing emotional capabilities exceeding his intended capacity, like that of the decommissioned "David" line. Noting the reactions of people around him to his unorthodox responses, Bishop decides that he is simply "different"

If you take the word of English Professor M Kieth Booker, then yes, Ash and - by extrapolation - all the later Androids are sentient.

From Ashs Wikipedia page
Emphasis mine

Like the alien organism itself, Ash (and indeed the sentient ship's computer, named "Mother") is presented as, in the words of M. Keith Booker, a "distinctive mode of intelligent existence that seems alien to our own", and is in fact (if one counts the dead pilot of the crashed spaceship) one of a number of sentient non-humans that humanity encounters in the film.

Also, Bishop is capable for emotion, from his Wikipedia page
Emphasis mine

Immediately after his activation, Bishop is quizzed by a technician named Dr. Sasaki to ensure he does not suffer from any potentially dangerous faults in his character programming. Sasaki releases Bishop into a room containing other similar androids, although she privately voices her concern that he may be flawed, possessing emotional capabilities exceeding his intended capacity, like that of the decommissioned "David" line. Noting the reactions of people around him to his unorthodox responses, Bishop decides that he is simply "different"

Also assuming the Mirriam Webster definition of "sentient", yes, they all are.

sen·​tient | \ ˈsen(t)-sh(ē-)ənt , ˈsen-tē-ənt
1: responsive to or conscious of sense impressions sentient beings
2: AWARE
3: finely sensitive in perception or feeling