My racknerd server is from this same deal last year. Here's how I set it up:
- TailScale-only traffic in. Any traffic is allowed out. Setup as exit node. Suddenly it's a personal-use-only VPN for when I'm on a public network. That's already worth $1 a month.
- Added Technitium DNS so I have an always on DNS-sinkhole. Set this as the DNS server for my whole tailnet so I can monitor all my internet traffic. Replaced my old NextDNS subscription (was $2 a month).
- Setup a Syncthing encrypted service running on the server. Then connected all my devices to each other with Syncthing-over-TailScale to give me a "dropbox replacement", with this RackNerd server acting as a source of truth since it's always online.
- Setup a CouchDB instance so I could run Obsidian-LiveSync with a centrally always-on computer.
- I setup two tiny web servers running on it. One has an encrypted html file that holds a picture of my passport. One has an encrypted html file that has part of my password for paypal. This is my insurance that even if I'm traveling and had my backpack stolen, I can always just use any internet-connected computer to prove who I am and move some money around.
Every time these days I want to run a service I always ask myself "do I need it always on?" and then set it up on my Racknerd VPS.
My next project might be a permanent link shortener service for my blog/personal use, so I can setup a personal permalink-type service.
Files: Filerun or File Browser both allow upload and download. I prefer the former as it allows me to preview file contents more broadly (e.g. pictures and videos). But it is paid.
Calendar: DecSync or Radicale both have no web UI. I prefer the former because it doesn't need a server at all, just a file sync solution. But, if you have an iPhone there are no clients and you'd have to setup a radicale server anyway.
Notes: Like others have said, Obsidian with Obsidian-livesync.
The nice thing about Filerun/DecSync/Obsidian is they store or serve files in close to their original format (e.g. files/xml/plaintext), so you can still open the file up on any computer and read its contents the way you normally would.