Here’s how to turn on Samba encryption on a share.

Edit /etc/samba/smb.conf on the Samba server.

[global]
server max protocol = SMB3
smb encrypt = required 
lanman auth = no

Edit /etc/samba/smb.conf on the Samba clients.

[global]
smb encrypt = required
client min protocol = SMB2
client max protocol = SMB3

To connect.

smbclient -e -m SMB3 //xxx.xxx.xxx.xxx/share-name -U username