Is there any proprietary Android app for which you wish there would be an open-source alternative?
Basically, what the title says. Do you use any app, that is proprietary, but either has no OSS alternatives or they're all not good enough? If there is an alternative, what keeps you from switching?
*You could create your own types of test (because sorry, not sorry, Anki sucks): Typing Practice, Multiple Choice, True/False, Fill-in-the-Blank, Matching, Short Answer.