I store it in paperless. I save it there for the longterm but also to have it ready when needed. If I guess I don't have internet. I save it on my phone as well.
On top of that, I use syncthing to sync the paperless files to my mobile phone. You can set storage path for each file in paperless; I have one for important files like tickets. Then I have them even without internet access 🙂👍
I also use email and company apps (flights, ..) .. 🫣
For movies I also use "note to self" in signal to quickly store and find them..