Hi there. So Electron embeds everything in a webview, which means that what you would have to develop would be a Node project most probably. Ionic does the same (kindof but won't bore you with specifics) but it does it much more efficiently. Usually you do Ionic apps with JS frameworks like Angular or React (this one recently added). Flutter on the other hand does native apps, it does it really good but it's support for Web is in beta and it's relatively simple to setup if you already know the SDK and the environment.
My recommendation would be that you do your app using Angular/Ionic if you reaaally need the multi-platform environment and there's different reasons in this case:
- Since it's a graduation project you need it to be as simple as it can be and adding a new technology adds to the learning curve.
- Flutter is great if you have different complex UI or if you have specific performance needs that require native support and in your case it does not seem like you need that.
- Flutter is also an incredibly powerful tool but it's learning curve might be tricky if you have not developed native apps before so I wouldn't recommend you start off like this if you have time sensitive projects like a graduation project. It does have great docs and an awesome community but I'd suggest you stick as close to what you know as you can.
- Ionic/Angular uses Typescript (a type javascript wrapper) and Angular (JS framework) so you will have to learn a little bit but if you already know HTML, CSS and Javascript you won't have that much of a hard time. Also there's quite a lot in terms of documentation and tooling already tested around this combination.
- Ionic/Angular has a really good CLI that helps you stick to the architecture they recommend so you wouldn't have to worry about it that much.
- Ionic/Angular helps you test either locally in the web browser as well as your devices which is in the end what you want if you are looking for a multi-platform system. Flutter also does this but is not quite in a stable state (yet!).
Anyway, in the end, if you go for the multi-platform suggestion I think, because of time you would be better off with Ionic. If you decide that you don't need that as of right now (which is fine as well) you can start with just the Android app and plan on the different things you might eventually need like a website or other different stuff. Cheers!