LR dual subs currently doesn’t officially work on tablets (iPad or otherwise) or phones.
Maybe one day!
Edit: Unless you’re using Turtle Tube via the website, according to one user: Do you want to enjoy LR extension through iPad? - #8 by erin_berndt
Link to mobile-compatible URL: https://www.languagereactor.com/phrasepump
Right now the dual subs feature only works via computers, but I know some have found success by using a different browser on the Ipad to try this out on.
Something to note is that this alternative browser is not currently supported by the devs so if you run into problems with it you would be on your own in troubleshooting with other members of the LR community that use the browser.
Additionally, using the Orion browser for LR on Netflix may be a bit tricker if it just forces you into the app version of Netflix vs the web browser version.