Keagan I just started ./vendor/bin/upgrade-carbon
This is not something you need to do. Flarum is currently using an old Carbon version, and this will be upgraded in a future Flarum release.
I can't tell if the error is linked to Carbon, it looks completely unrelated.
Is it a recent Flarum install ? Did you do something else prior to the error ? Can you share the output of php flarum info ?
To revert the Carbon update, you should be able to edit composer.json, remove any line about Carbon in require, then run composer update nesbot/carbon. I have not tested it but this should get you back to the most recent but-still-outdated Carbon version we use.
