I use Obsidian with self-hosted live-sync from here: https://github.com/vrtmrz/obsidian-livesync/

Basically you have a couchDB hosted in your homelab to store your obsidian data and then the obsidian self hosted live sync plugin that runs on your devices connects to your self hosted database and sync your notes there in an optimized. I tried both this and sincronizing via github and I prefer this, because is faster and less intrusive

A mix of cost (questionable), education (less questionable) and coolness (not questionable)

LLDAP is the simplest and covers most basic needs.