Jan 19 16:09:37 example.com httpd[18864]: (13)Permission denied: AH00091: httpd: could not open error log file /mytest/logs/error_log.

Smells like a selinux issue. That's not the normal place that Apache is allowed to write logs. I'd suggest moving the log to /var/log/apache/vhost0 or something similar.

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/using_selinux/configuring-selinux-for-applications-and-services-with-non-standard-configurations_using-selinux

https://www.serverlab.ca/tutorials/linux/web-servers-linux/configuring-selinux-policies-for-apache-web-servers/