Blank page after login

Hello!
Ispconfig version 3.2
Debian buster
Apache 2.4.38
I am using multiple versions of PHP and followed the instructions with the sury.org repository to install all versions from 5.6 to 8.0.
I am using update-alternatives and a2dismod / a2enmod to change PHP version. I am in PHP7.4 on the server by default.
After updating diferent version of PHP, ISPConfig could be opened, I added a new version PHP8.0 under System> Additional PHP Versions.
Since then I get the ISPConfig logo displayed and the logout-admin button.

I found the same report, but it asks me to revert to the default PHP version with no result. Report link here

Code:

1/ result of the command php -v on the server:

PHP 7.4.16 (cli) (built: Mar 5 2021 08:36:10) (NTS)
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
with Zend OPcache v7.4.16, Copyright (c), by Zend Technologies.

2/ phpinfo on a site: PHP Version 7.4.16 same version as on the server.

3/  result of the command php --ini on the server:
Configuration File (php.ini) Path: /etc/php/7.4/cli
Loaded Configuration File:         /etc/php/7.4/cli/php.ini
Scan for additional .ini files in: /etc/php/7.4/cli/conf.d
Additional .ini files parsed:      /etc/php/7.4/cli/conf.d/10-mysqlnd.ini,

4/ phpinfo sur l'interface Ispconfig
PHP Version 8.0.3.
 

I cannot force the management interface of Ispconfig to switch to php7.4
There seems to be a compatibility issue with version 3.2 of Ispconfig and PHP8.0.
Thank you in advance for your answers.