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Problem: Vino by default requires TLS authentication in order to encrypt the password. Remmina on the other hand does not support that. The only common method is plaintext passwords.
Solution: quite simple actually, we need to disable encryption on the server side:
sudo apt-get -y install dconf-tools dconf write /org/gnome/desktop/remote-access/require-encryption false /usr/lib/vino/vino-server --sm-disable start
A word of caution: Now before you do this, be aware, that after following these steps, the vnc password travel through the network in clear text. not something you should do in an untrusted network (yes, the internet for example). I recommend using an ssh tunnel for your vnc connections over such networks.
in order to enforce using an ssh tunnel you could run
gsettings set org.gnome.Vino network-interface lo
this only allows connections from the localhost and therefore forces external pc's to use an ssh tunnel.