I use a currently fully updated Armbian on an ODROID-C2. 

 

I start tigervnc like this in /etc/crontab:

 

@reboot linuxfan bash -lc 'vncserver -local host no'

 

My ~/.vnc/xstartup:

 

#!/bin/bash

exec startxfce4

 

Everything works over VNC but gparted. Nothing would happen when I click on the menu entry. When I try to start it from an Xfce terminal, it (somehow) tells my why it won't start:

 

$ sudo gparted

No protocol specified

 

(gpartedbin:23385): Gtk-WARNING **: 20:55:09.777: cannot open display: :1.0

 

I'm at my wits end and would be glad if someone can help me out.

Maybe you ought to try http://xrdp.org/

A tutorial: https://linuxize.com/post/how-to-install-xrdp-on-debian-10/

VNC isn't secure. A way to secure VNC would be to tunnel the connection through SSH and such configuration is much more frustrating.
XRDP on the other hand runs very smoothly on most machines, you shouldn't run into issues when you have no Display jacked in and you're able to secure the connection with SSL/TLS

I'm not that experienced with XRDP or VNC but my headaches are decreasing since using XRDP ^^

 

I remember I have ran gparted without issues on other Linux distros over VNC. It never complained like this.

Same here. I had very good times with VNC too.