Steps to reproduce:
1. Add the following config for notifications:
https://doc.ibexa.co/en/latest/administration/back_office/notifications/#notification-timeout
2. Set success to 0.

3. Create any content type and publish it.

Expected result:

Success notification message stays in the back office until you close it.

Actual result:

Success notification disappears after 5 seconds.

Comments:

Following marek.nocon@ibexa.co's comment, the problem is in https://github.com/ibexa/admin-ui/blob/main/src/bundle/DependencyInjection/Configuration/Parser/Notifications.php#L44
for value '0', the function returns 'true' and skips this setting:
               if (!isset($config[$key]) || empty($config[$key])) {