I use syncthing to sync files between phone, pc and server.
The server runs proxmox, with a proxmox backup server in VM. A raspberry pi pulls the backups to an usb ssd, and also rclone them to backblaze.
Syncthing is nice. I don't backup my pc, as it is done by the server. Reinstalling the pc requires almost no preparation, just set up syncthing again
Like most others I use paperless-ngx.
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..