Softaculous is renowned for installing dodgy copies of Magento. I can see now why you keep running into issues. It “forces” Magento to install, but doesn’t configure the server to meet the requirements that Magento needs in order to run properly. So, everyone ends up running into issues.
For example, Softaculous does not configure your web server to install and enable all of the required PHP Modules as listed in the Official Magento Documentation. Going through this documentation should help backfill some of the issues that Softaculous has caused.
One of the missing/disabled PHP modules could be something called “fileinfo”, which is responsible for validating file types - This is causing the error you’re reporting.