there need to add one command before:
chmod -R 777 /var/lib/tftpboot/uefi
systemctl enable --now tftp.socket

I wasted two days because of this.

Reported by: 2281551151

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/performing_an_advanced_rhel_8_installation/preparing-for-a-network-install_installing-rhel-as-an-experienced-user#annotations:ffe9d78f-20ed-4773-81a9-7a2bbf02ff07