If you have a tablet and want to use vocabtracker, there is unfortunately no app yet (in development, maybe a 2023 release or so Ive heard), however you can use vocabtracker in the device browser, as well as the extension in browsers such as Kiwi (so you can read ebooks using neat-reader as mentioned in previous posts). One problem with this is a lack of out-of-the box sentence selection since selecting more than one word on a touch screen results in a pop-up menu that doesnt register the words with the vocabtracker sidebar (known but unsolved problem for the VocabTracker team). One workaround I have found is to connect a bluetooth mouse to the table/phone which allows for sentence select to work like on a pc.