Update, remove or redirect the appearance menu item.
<?php
return [
'wp-admin.$role|$username' => [
'appearance',
'appearance' => (string) $route,
'appearance.title' => (string) $title,
'appearance.icon' => (string) $dashicon,
],
];
Remove from menu;
<?php
return [
'wp-admin.$role|$username' => [
'appearance',
],
];
Remove from menu and enforce a page redirect;
<?php
return [
'wp-admin.$role|$username' => [
'appearance' => 'posts',
],
];