Is there a way to run hook_form_alter after themes implementation? I'm using the material_admin theme, which has a hook_form_alter()  implementation.

I see that my module's hook_form_alter() is executed before the theme hook. Both hooks are editing the same form property, so the change done in my code is always overridden.

In my hook_module_implements_alter() implementation I see only the modules that implement hook_form_alter(). The theme's implementation is not there.

How can I control its execution?
I think you cannot have a module hook executed the same hook implemented by a theme. If we look at the hook invoking code, we see that the theme hooks are invoked separately and after the module hooks.

The best bet would be to remove it from the theme and put it in a module, or trying with #after_build.

FormBuilder.php contains the following code.

$this-&gt;moduleHandler-&gt;alter($hooks, $form, $form_state, $form_id);
$this-&gt;themeManager-&gt;alter($hooks, $form, $form_state, $form_id);