Admin setting - System shows [Internal Server Error]

Hi,
I’m using the NC 21.0.2 with following configuration:
Operating system: Linux 4.18.0-240.22.1.el8_3.x86_64 #1 SMP Thu Apr 8 19:01:30 UTC 2021 x86_64
Webserver: nginx/1.20.1 (fpm-fcgi)
Database: mysql 8.0.25
PHP version: 8.0.6
Nextcloud version: 21.0.2 - 21.0.2.1

And when I try to open [mydomain]/settings/admin/serverinfo, the error displays as follows:
Internal Server Error
The server was unable to complete your request.
If this happens again, please send the technical details below to the server administrator.
More details can be found in the server log.

Technical details

  • Remote Address: ******
  • Request ID: 5vdtNHGKku62AkPFrU5c

And I found these error in log:

Exception: Call to undefined function OCA\ServerInfo\OperatingSystems\shell_exec()
/data/wwwroot/cloud.facfox.com/lib/private/AppFramework/App.php - line 157:

OC\AppFramework\Http\Dispatcher->dispatch()

/data/wwwroot/cloud.facfox.com/lib/private/Route/Router.php - line 302:

OC\AppFramework\App::main()

/data/wwwroot/cloud.facfox.com/lib/base.php - line 993:

OC\Route\Router->match()

/data/wwwroot/cloud.facfox.com/index.php - line 37:

OC::handleRequest()

Is that caused by PHP8 version I installed? Any one can