Index: src/wp-admin/includes/post.php
===================================================================
--- src/wp-admin/includes/post.php	(revision 43852)
+++ src/wp-admin/includes/post.php	(working copy)
@@ -2096,6 +2096,16 @@
 					continue;
 				}
 
+				// If a meta box is just here for back compat, don't show it in the block editor.
+				if ( isset( $meta_box['args']['__back_compat_meta_box'] ) && $meta_box['args']['__back_compat_meta_box'] ) {
+					continue;
+				}
+
+				// If a meta box doesn't work in the block editor, don't show it in the block editor.
+				if ( isset( $meta_box['args']['__block_editor_compatible_meta_box'] ) && ! $meta_box['args']['__block_editor_compatible_meta_box'] ) {
+					continue;
+				}
+
 				$meta_boxes_per_location[ $location ][] = array(
 					'id'    => $meta_box['id'],
 					'title' => $meta_box['title'],