Basically, you can use my notebooks in all note-taking apps that allow importing your own templates. Although I design templates and notebooks especially for the use with GoodNotes, I have tested them with several apps. They work just fine with note-taking apps like Notability, Tayasui Memopad (free) and some sketching apps like ProCreate, Tayasui Sketches, Adobe Sketch (free) and Paper 53 (free).
Currently testing with: Notes Plus. Apps that don’t work at the moment: Moleskine and INKredible (don’t allow importing own templates), Bear Writer (doesn’t allow to write on images or import templates).
If you use an app I haven’t tested yet, just drop me a line and I will let you know if it’s working.