Hello,
I installed:
t4-system-plugin_2.5.4 and tpl_t4_bs5_blank_1.3.0
When I activate t4_bs5_blank – Default in Styles, I get this error in the frontend:
Deprecated: T4\MVC\Router\T4::__construct(): Implicitly marking parameter $app as nullable is deprecated, the explicit nullable type must be used instead in /home/mondossier/public_html/monsite/plugins/system/t4/src/t4/MVC/Router/T4.php on line 82
Deprecated: T4\MVC\Router\T4::__construct(): Implicitly marking parameter $menu as nullable is deprecated, the explicit nullable type must be used instead in /home/mondossier/public_html/monsite/plugins/system/t4/src/t4/MVC/Router/T4.php on line 82
After correcting line 82
By replacing:
public function __construct(SiteApplication $app = null, AbstractMenu $menu = null)*
with :
public function __construct(?SiteApplication $app = null, ?AbstractMenu $menu = null)
I now have a blank page in the frontend!
In the backend, the Global Configuration page is not displaying correctly :

Is T4 Framework compatible with Joomla 6?
If so, what should I do?
Joomla! 6.0.3
PHP Version 8.4.18