Answer for Acorn and Radicle by Roots

In my case, the artisan command (in this case, aliased by wp acorn) did not work because it couldn't get over the loss of the provider in order to clear the cache:

$ wp acorn cache:clear

In ProviderRepository.php line 206:

  Class "BladeUI\Icons\FactoryServiceProvider" not found

So after ensuring the provider wasn't listed in composer.json (extra>acorn>providers key) and config/app.php (providers key), we must manually remove the cache like so:

rm -rf storage/framework/cache/packages.php

It may also be necessary to do composer dump-autoload.