Yes you are right, the option is only available for free events. I believe some payment processor will need confirmation page(incase of paypal express) hence the option is always hidden for paid events.
You can try installing skip confirmation page extension, this should show the Use a confirmation screen? option for you for paid and free events.
You may want to have a look at our new extension "Event Messages". It provides an alternative way to send confirmation emails for CiviCRM Events. It creates an additional tab within CiviCRM Events that allows you to define different message templates to be sent based on conditions (including the participants status, role and preferred language). It ...
If you mean to turn off Confirmation screen for Events by default when an Event is created then you can either
Implement pre hook to set is_confirm_enabled = 0 when $op is create and Objectname is Event
Run below sql query
ALTER TABLE civicrm_event CHANGE is_confirm_enabled is_confirm_enabled TINYINT(4) NULL DEFAULT '0' COMMENT 'If false, the event ...
Do you refer to the sendeventconf extension that can be found at https://github.com/TechToThePeople/sendeventconf ?
It's a basic extension and it most likely works. So, it makes sense to try. Installation of an extension not found on the list is documented at https://docs.civicrm.org/sysadmin/en/latest/customize/extensions/#installing-a-new-extension. You ...
Most probably, AdminTools by Akeeba is blocking a request.
Please try to deactivate
PHP stream wrappers block (PHPShield)
Direct File Inclusion shield (DFIShield)
PHP session data poisoning protection (SessionShield)
from the WAF/Request Filtering section or temporarily deactivate AdminTools.