In another forum, forum.developer.nvidia.com, "nekokeitai" wrote something which worked for me. These commands can be used via ssh on the remote Ubuntu 18.04 PC:

Install vino:

sudo apt install vino

Find the UUIDs of your connections and use them as a comma separated list inside the square brackets of the last configuration line. I have only tried one UUID inside the single quotes, though:

nmcli connection show

Configure vino:

gsettings set org.gnome.Vino prompt-enabled false
gsettings set org.gnome.Vino require-encryption false
dconf write /org/gnome/settings-daemon/plugins/sharing/vino-server/enabled-connections "['']"

Start vino:

export DISPLAY=:0 && /usr/lib/vino/vino-server

Now, on the local PC use remmina with VNC protocol to connect to the remote PC.

Here is some scripts I use to install vino onto remotes.

Within a main setup script I will just include the code that calls the vnc_access script (which is in a subdirectory 'vnc' but change this to wherever you put the 2nd script.

if [ ! -z "$install_vnc" ] ; then
    user_password='password'
    vnc_password='password'
    vnc_script="${BASH_SOURCE%/*}/vnc/vnc_access.sh"

    printf '\n\tSetting up vino-server on host...\n' >&2

    ssh $host_user_name@$host_address \
        "bash -s" < "$vnc_script" $user_password "'$vnc_password'"

    printf '\n\tDone sending vnc to host.\n' >&2
fi

And here is the vnc_access.sh script

#!/bin/bash
#
# Tools to enable and configure vino for vnc access

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# parse arguments
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
user_password=$1
vino_password=$2

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# initialize values
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vino_password_binary="$(echo -n ${vino_password} | base64)"

declare -A settings
settings[alternative-port]="uint16 5900"
settings[authentication-methods]="['vnc']"
settings[disable-background]=false
settings[disable-xdamage]=false
settings[enabled]=true
# enum 'never' 'always' 'client'
settings[icon-visibility]="'client'"
settings[lock-screen-on-disconnect]=false
settings[mailto]="''"
settings[network-interface]="''"
settings[notify-on-connect]=true
settings[prompt-enabled]=false
settings[require-encryption]=false
settings[use-alternative-port]=false
settings[use-upnp]=false
settings[view-only]=false
settings[vnc-password]="'$vino_password_binary'"

# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# main
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# We need to have sudo enabled to do many of these tasks, 
#  this is a bit of a hack, but it gets the job done.
printf "Enabling sudo privileges...\n" >&2
echo $user_password | sudo -S whoami >/dev/null
printf "\n" >&2

# If vino is not installed, install it
if [ -z "$(dpkg -l | egrep -i 'vino')" ] ; then
    printf "Installing vino...\n" >&2
    sudo apt-get update
    sudo apt-get install -y vino
fi

# Make sure we are performing these operations of the remotes display.
printf "Forwarding X org Display...\n" >&2
export DISPLAY=:0
sudo xhost +

# Loop through settings and configure vino.
for setting in "${!settings[@]}" ; do
    current_value="$(gsettings get org.gnome.Vino "$setting")"
    to_value="${settings[$setting]}"
    if [[ "$current_value" != "$to_value" ]] ; then
        printf "changing Vino's ${setting} from ${current_value} to ${settings[$setting]}\n" >&2
        DISPLAY=:0 sudo gsettings set org.gnome.Vino "$setting" ${settings[$setting]}
    fi
done

# Vino requires a reboot to work. If someone can find out how to do this with
#  out rebooting or logging out, let me know.
sudo reboot