/etc/resolv.conf is missing after installation of RHEL 8
By default, NetworkManager on Red Hat Enterprise Linux (RHEL) 8 dynamically updates the
/etc/resolv.conffile with the DNS settings from active NetworkManager connection profiles.
If you don't want dynamic updates by NetworkManager set
[main]
dns=none
in /etc/NetworkManager/conf.d/90-dns-none.conf
and reload the NetworkManager with
systemctl reload NetworkManager
The procedure is documented in more detail in the RHEL 8 documentation