Do I always need to indicate in my works-cited-list entry that a work I am citing was streamed through an app?
No. If the app is the work, as in the following examples, you do not need to indicate in your works-cited-list entry that you are citing an app:
Shakespeare, William. The Tragedy of Othello. Edited by Barbara Mowat and Paul Werstine, version 1.3.1, Luminary Digital Media, 2013.
Laudate. Version 2.36, Aycka Soft, 28 Feb. 2018.
There is also no need to indicate that you are citing an app if the app is simply the platform through which you accessed the work. For instance, if you watched the movie The Crown using the Netflix app, you could cite the work as follows:
The Crown. Left Bank Pictures / Sony Pictures Television Production UK, 2016.
If, however, the work exists in another medium and you know that the app version differs, you should indicate that you are citing an app. As explained in a previous post, an app is a version according to the MLA format template. Thus, if you know that the version of The Crown watched through the Netflix app differs from the version shown in theaters, list “Netflix app” in the “Version” slot:
The Crown. Netflix app, Left Bank Pictures / Sony Pictures Television Production UK, 2016.