The Dropbox service prevents a proper reboot on Arch Linux

Thanks for the detailed report and investigation mnrzghi​ 

We’ve seen similar issues before when Dropbox is installed via unofficial third-party packages like the AUR or Flatpak versions. These community-maintained builds often define their own systemd service files, and in some cases, they may not shut down cleanly or manage Dropbox's lifecycle in the expected way.

If you're using the AUR version, this might be caused by the systemd service starting the Dropbox launcher instead of the actual daemon. Without a properly defined ExecStop, systemd doesn't know how to stop Dropbox cleanly during shutdown, which can lead to the behavior you're seeing.

Here are a couple of things you can try:

• Switch to the official Dropbox package:
  We recommend using the official installation instructions here:
  👉 https://www.dropbox.com/install-linux
  This version avoids potential systemd-related issues and is what we test against internally.
• Avoid unofficial Flatpak builds:
  For reference, the Flatpak version available on Flathub is not maintained or supported by Dropbox:
  https://flathub.org/apps/com.dropbox.Client
• If sticking with the AUR:
  You might want to review or modify the systemd service file to either:
  • Start the Dropbox daemon directly (instead of the launcher), if using Type=simple, or
  • Add an appropriate ExecStop directive to ensure Dropbox shuts down gracefully.
    
    

That said, please note that Arch and community packages like the AUR aren't officially supported by Dropbox, so you may want to report this issue directly to the AUR package maintainer as well.