The most obvious answer. It is a little resource heavy though, so you would need at the very least a Pi 3, better a Pi 4.

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This is what I run, but I run it on my media center which is real full workstation hardware since it runs media center stuff, plus all of my home server stuff. Nice thing about next cloud is you can use it to sync contacts, calendars, todos, Joplin, as well as just the box type storage application.