OnSong and forScore are just two different programs in a related space, and both are the envy of users of other platforms. There are solutions on Android, and they work...but these two programs are exceptional.
OnSong has its background as a tool for worship leaders, first and foremost, as a way to display, edit, and share lyrics for themselves AND their congregations. The program can actually be used to display lyrics on a background on a screen, with a different view than the band. Ultimately, OnSong is about working with what I call "chord charts." For many ukulele players, to be able to import a "song sheet" and then edit it to match how you want to play it, and then display it/share it is pure gold. I get it.
forScore is a musician's PDF reader with a ton of tools. While it can display PDFs of songs in "chord chart" format (which is what so many people use), it can also be used to display music that has been printed as a PDF (music notation as a font) or scanned (as an image). For a person like myself, a music teacher, a classically trained music (i.e. I read music notation as a primary way of understanding music), and as a performer, forScore is invaluable to me.
As I make the play alongs, I've been working with Ukutabs lately to put a "Chord Chart" of every new chord on their page. I prepare my scores in an app called Song Sheet Pro, then export to OnSong, which allows me to export that file to a .TXT file that can be used on Ukutabs.
There are undoubtedly more features and uses of OnSong...and forScore's tools for a musician and as a music teacher are massive. I'm just happy that we have both programs available at a very affordable cost. We're lucky.
Side note: StaffPad, a music notation program originally created ONLY for Microsoft Surface, came out on iPad a few weeks ago. I'd still recommend Notion for most users if you want to create music notation on an iPad.