In collaboration with @DrCWO I would like to announce roo6D, a plug-and-play solution for the 3Dconnexion SpaceMouse Wireless and Raspberry Pi4. It is called roo6D in reference to the 6 degrees of freedom that a space mouse offers:
Many improvements went into this product, including better zone handling, support for incremental volume control and improved configurability.
RooExtend website: https://rooextend.com
roo6D: Run Roon With SpaceMouse® Wireless
roo6D is compatible with 3Dconnexion SpaceMouse Wireless, SpaceMouse Compact, SpaceNavigator, SpaceMouse Pro and SpaceMouse Pro Wireless.
A version supporting the wired 3Dconnexion SpaceNavigator and SpaceMouse Compact is still available in the Roon Extension Manager 1.x and on Github: GitHub - KlausDEngel/roon-spacenav: A volume control Roon extension for the SpaceNavigator space mouse.