Completely removing cache I've set $settings['cache']['bins']['render'] = 'cache.backend.null; and $settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null; in local.settings.php, but I’m having a hard time dumping variables out to a page from a hook that runs once early on (hook_entity_bundle_field_info_alter()). If I do a simple var_dump (or dpm, etc.)  from here, variables will show up when running drush cr in the console, but not when hitting a new page in the browser afterwards. Does anyone know how I can set up debugging so I'm able to look at these variables in the browser?
What you did only uses the null backend render cache bins.

Field definitions are cached in the discovery bin, you either have to set that to null as well, but that will make your site very slow. You can also simply truncate cache_discovery manually in the database and then do another request in the browser.