For me, Google video search, Google books (Internet Archive is good, but doesn’t always have the same stuff), Adobe InDesign (but in the process of learning LaTeX), and Typewise. As for the Google stuff, I liked Whoogle a lot, but almost all their instances seem to have been blocked or shut down. Also, apologies if this is repeating an earlier post.
I think it would depend on the music player? There is listenbrainz-ios, but I assume it’s banned by Apple because it’s opensource? That would make iOS pretty bad if you want to go opensource with stuff. But if you’re in the EU, that might change soon thanks to the DMA which will force Apple to allow third-party stores of which probably a few opensource ones will pop up.
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There’s a TestFlight link. Thanks!