Self-Hosted Sync Tools
Change a file on one device and it updates on the others. These tools sync folders continuously, keep previous versions in case of mistakes and work across Windows, macOS, Linux and mobile.
Joplin
Sync notes between the official Joplin desktop and mobile apps using a server kept on your own network.
Free for personal usex86 + ARMNode.js
Seafile
Faster than Nextcloud, private as Dropbox should be, with block-level file synchronization on your own hardware.
Free + Prox86 + ARMC
Syncthing
Continuous, encrypted file synchronisation between your own devices, with no central server holding your files.
Freex86 + ARMGo