LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Failed to execute child process "dbus-launch" (No such file or directory) while x-forwarding

The solution to this issue was to install 'dbus-x11'.

sudo apt-get install dbus-x11

I came to this solution by looking for similar issues.

I've found Pablo Saratxaga's answer on Serverfault, suggesting a script for a similar issue.

https://serverfault.com/a/673837/409813

I've thought it would be worth to run

export $(dbus-launch)

because this is the main command that the script is starting.

The error message from the output is the following.

The program 'dbus-launch' is currently not installed. You can install it by typing: 
apt install dbus-x11

I installed dbus-x11 and x-forwarding started to work without showing an error message.