Uncaught PHP Exception: MissingValueContextException
It seems to be related to a new constraint added on releases, as seen on https://www.drupal.org/project/drupal/issues/3113474
As &quot;view mode&quot; is asked, with no default context, some modules like Panels IPE, Panels, MiniLayout may generate problems if you ask to display a single entity field as FieldBlock.
Just apply patch on https://www.drupal.org/files/issues/2020-02-13/3001313--63_0.patch ; for the record :

--- a/core/modules/layout_builder/src/Plugin/Derivative/FieldBlockDeriver.php
+++ b/core/modules/layout_builder/src/Plugin/Derivative/FieldBlockDeriver.php
@@ -124,7 +124,14 @@ public function getDerivativeDefinitions($base_plugin_definition) {
           $context_definition->addConstraint('Bundle', [$bundle]);
           $derivative['context_definitions'] = [
             'entity' => $context_definition,
-            'view_mode' => new ContextDefinition('string'),
+            'view_mode' =>  new ContextDefinition(
+              'string',
+              $this->t('View Mode'),
+              FALSE,
+              FALSE,
+              NULL,
+              'default'
+            ),
           ];