Yes, you can create an open wifi network access point without implementing security protocols using nmcli and NetworkManager. Use the following command
nmcli connection add \
type wifi \
con-name "My Hotspot" \
autoconnect no \
wifi.mode ap \
wifi.ssid "My Hotspot" \
ipv4.method shared \
ipv6.method shared
Note the non-inclusion of the password parameter when creating the connection. Inclusion of the parameter when the connection is built creates a distinctly different connection profile which includes the 802-11-wireless-security section which forces WPA or WEP. Once a profile is formed, I don't believe it can be changed, so if you may need two profiles if you want to switch between secure and insecure.
Along these same lines, folks are trying to bridge wifi to ethernet. AFAIK you cannot change a wifi connection profile after it is created to include the bridge as it won't contain that section, so to create an open wifi bridged access point include the "master" parameter.
nmcli connection add \
type wifi \
master br0 \
con-name "My Hotspot" \
autoconnect no \
wifi.mode ap \
wifi.ssid "My Hotspot"
After bridging wifi you may have difficulties with the wpa_supplication and may need to specify the bridge interface on the command line, systemd, or arguments file. For CentOS8 this was in /etc/sysconfig/wpa_supplicant
--INTERFACES=""
++INTERFACES="-i wlp2s0 -b br0"