Change the default theme

config/default/block.block.opdavies_abouttheauthor_2.yml

@@ -0,0 +1,30 @@
+uuid: a3a4c380-0449-4e0e-b53d-d739c6d94a9c
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+  theme:
+    - opdavies
+id: opdavies_abouttheauthor_2
+theme: opdavies
+region: content
+weight: 0
+provider: null
+plugin: 'block_content:cec72fa5-49c4-428d-bf49-59b477c9e886'
+settings:
+  id: 'block_content:cec72fa5-49c4-428d-bf49-59b477c9e886'
+  label: 'About the Author'
+  provider: block_content
+  label_display: visible
+  status: true
+  info: ''
+  view_mode: full
+visibility:
+  node_type:
+    id: node_type
+    bundles:
+      post: post
+    negate: false
+    context_mapping:
+      node: '@node.node_route_context:node'