Does Mobaterm support RDP? I don't know Mobaterm just saw it in some Teams meetings with colleagues from India.
However, in VBox manual it is promised that RDP can be used after installing some required VBox extension.
Please note that extension packages for VBox are not opensource - as VBox itself - and can be only used by paying for them or for private usage!
https://www.virtualbox.org/manual/ch03.html#settings-display
3.6.2. Remote Display Tab
On the Remote Display tab, if the VirtualBox Remote Display Extension (VRDE) is installed, you can enable the VRDP server that is built into Oracle VM VirtualBox. This enables you to connect to the console of the virtual machine remotely with any standard RDP viewer, such as mstsc.exe that comes with Microsoft Windows. On Linux and Oracle Solaris systems you can use the standard open source rdesktop program. These features are described in Section 7.1, “Remote Display (VRDP Support)”.
Enable Server: Select this check box and configure settings for the remote display connection.