Attempted both the fresh install and the update, both did nothing to resolve.
EDIT: Wanted to make sure, so I double-checked my php/mysql version, both are sitting past 5.5 as needed.
Transcript from composer update:
Loading composer repositories with package information
Updating dependencies (including require-dev)
- Removing flarum/composer-installer (v0.1.0)
- Installing flarum/composer-installer (v0.2.0)
Downloading: 100%
Writing lock file
Generating autoload files
Checked the composer.json after the update, and I'm honestly not sure if "flarum/composer-installer": should still be at version ""
"flarum/composer-installer": "*",
If there's anything else I can add to help debug, please let me know.