Install Gin via farm_ui_theme_install() instead of config/install.

farm.info.yml

@@ -17,4 +17,4 @@ dependencies: {  }
 install:
   - dblog
 themes:
-  - gin
+  - claro

farm.install

@@ -7,6 +7,15 @@
 
 use Drupal\Component\Serialization\Json;
 
+/**
+ * Implements hook_install().
+ */
+function farm_install() {
+
+  // Use private file system by default.
+  \Drupal::configFactory()->getEditable('system.file')->set('default_scheme', 'private')->save();
+}
+
 /**
  * Implements hook_install_tasks().
  */

modules/ui/theme/farm_ui_theme.info.yml

@@ -1,8 +1,7 @@
 name: farmOS UI Theme
-description: Provides Gin theme overrides for farmOS.
+description: Install Gin theme and provide overrides for farmOS.
 type: module
 package: farmOS UI
 core_version_requirement: ^9
 dependencies:
-  - config_rewrite:config_rewrite
   - drupal:block

modules/ui/theme/farm_ui_theme.install

@@ -0,0 +1,63 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the farm_ui_theme module.
+ */
+
+use Drupal\block\Entity\Block;
+
+/**
+ * Implements hook_install().
+ */
+function farm_ui_theme_install() {
+
+  // Install the Gin theme and make it the default.
+  \Drupal::service('theme_installer')->install(['gin']);
+  \Drupal::configFactory()->getEditable('system.theme')->set('default', 'gin')->save();
+
+  // Load Gin settings.
+  $gin_settings = \Drupal::configFactory()->getEditable('gin.settings');
+
+  // Use vertical toolbar.
+  $gin_settings->set('classic_toolbar', 'vertical');
+
+  // Use green/orange color palette.
+  $gin_settings->set('preset_accent_color', 'green');
+  $gin_settings->set('preset_focus_color', 'orange');
+
+  // Use farmOS logo and favicon.
+  $gin_settings->set('icon_default', FALSE);
+  $gin_settings->set('icon_path', drupal_get_path('module', 'farm_ui_theme') . '/logo.png');
+  $gin_settings->set('favicon.use_default', FALSE);
+  $gin_settings->set('favicon.path', drupal_get_path('module', 'farm_ui_theme') . '/favicon.ico');
+
+  // Save Gin settings.
+  $gin_settings->save();
+
+  // Create the "Powered by farmOS" block.
+  // This must be done in hook_install() instead of config/install because Gin
+  // needs to be installed first.
+  $values = [
+    'id' => 'farm_powered',
+    'plugin' => 'farm_powered_by_block',
+    'theme' => 'gin',
+    'region' => 'content',
+    'weight' => 1000,
+    'settings' => [
+      'id' => 'farm_powered_by_block',
+      'label' => t('Powered by farmOS'),
+      'provider' => 'farm_ui_theme',
+      'label_display' => '0',
+    ],
+    'visibility' => [],
+    'dependencies' => [
+      'enforced' => [
+        'module' => [
+          'farm_ui_theme',
+        ],
+      ],
+    ],
+  ];
+  Block::create($values)->save();
+}