Process class relies on proc_open, which is not available on your PHP installation.

proc_open-solve.php

It is because of Flare error reporting service enabled in debug mode
There is a workaround for this.

Publish flare config file
php artisan vendor:publish --tag=flare-config

and in config/flare.php

Set

'collect_git_information' => false 
'reporting' => [
        'anonymize_ips' => true,
        'collect_git_information' => false,
        'report_queries' => true,
        'maximum_number_of_collected_queries' => 200,
        'report_query_bindings' => true,
        'report_view_data' => true,
    ],
Thanks you very much! ♥