I know it is not fully in the scope, but I will describe my case, and I hope that this will give you some ideas and hits. I am working on an application that monitors elderly people in non-intrusive way. Their children install the application on their device and they do nothing with it. It follows the 'install and forget' principle. Don't bother them for anything. No notifications, no need to open it. If opening is needed, it is because they are curious, not because it is needed. All the information/notifications goes to their children. You can think in that direction. Can you make it a desktop application? In that case, you don't need authentication. It is actually simpler for them, because, instead of opening the browser, typing the URL, they just double click the icon. You can make a update mechanism that silently adds new features and bug fixes.

Some control can be added automatically from a server, so that they don't need to do anything.

The main problem here is, when they search for attention. I understand them and being respectful and giving them attention is a good thing, but from software support point of view, this is hard to be minimized.