These instructions were tested on OpenSUSE Leap 15.3 with RemoteBox 3.0, other configurations may vary.
They describe installing the RemoteBox client and assume you have root privileges to perform the install. In order to connect from RemoteBox, VirtualBox will need to be installed and configured on the server and if necessary, appropriate firewall ports will need to be opened.
RemoteBox is available in the official OpenSUSE repositories which may be sufficient for your needs, although the version may differ from the latest. It can be installed as follows:
zypper install remotebox freerdp tigervnc
If you have not done so already, you'll need to ensure an additional Perl repository is enabled. This can be done as follows, remembering to change the version number as appropriate for your version of OpenSUSE.