Ask HN: How do you organize your important files?

TL;DR: By curiosity, which system/software do you use to manage your important files?

I use my computer and phone to manage important files like paysheets, official documents etc... It's useful to have the files on several devices and rely on duplication to ensure they are not lost. I currently use Google Drive, but I want to get rid of Google, and I'm hesitating between two options :

- use syncthings (https://syncthing.net/), but I might delete a file by accident and lose it forever, which I don't like

- use git (ability to have mirrors and control very carefully each file modification), but it might be cumbersome, and these important files are almost always heavy PDFs, so I'm not sure it's the correct tool

I also have a NextCloud server, but I'm not sure I will still maintain it in 10 years