Quite some work done here.

src/Tech/Service/UserChecker.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Tech\Service;
+
+use App\Tech\Entity\User;
+use Symfony\Component\Security\Core\Exception\CustomUserMessageAuthenticationException;
+use Symfony\Component\Security\Core\User\UserCheckerInterface;
+use Symfony\Component\Security\Core\User\UserInterface;
+
+class UserChecker implements UserCheckerInterface
+{
+    public function checkPreAuth(UserInterface $user): void
+    {
+        if (!$user instanceof User) {
+            return;
+        }
+
+        if (!$user->isVerified()) {
+            throw new CustomUserMessageAuthenticationException('Your email address is not verified.');
+        }
+    }
+
+    public function checkPostAuth(UserInterface $user): void
+    {
+    }
+}