iPad VNC cannot access Ububtu / disabling the encryption completely on Vino server

https://linuxconfig.org/ubuntu-remote-desktop-18-04-bionic-beaver-linux

From this reason we first need to disable encryption on remote Vino desktop sharing server. Execute the following linux command to disable the remote server to require an encryption for connecting VNC clients:

$ gsettings set org.gnome.Vino require-encryption false

Confirm that the encryption on your remote server is disabled:

$ gsettings list-recursively org.gnome.Vino | grep encrypt
org.gnome.Vino require-encryption false

Given that the encryption is now disabled, to add some level of privacy you may optionally first create SSH tunnel to your remote desktop for your VNC client on port 5900 before making VNC connection.