Okey, Its working now!!!
for everybody struggling with same issue, Ive commented out lines 804-816 in Assets/realvirtual/private/RuntimeUI/SceneMouseNavigation.cs and also in line 150, changed EnableSpaceNavigator = true
-> false. 
Seem to work fine. Even in unity game mode mouse navigation seem to work like it was meant to work.

Hi
Ive encountered the simmilar issue while importing realvirtual starter to my Unity 6.0.61 URP, empty project on ubuntu 22.04. After import i get the error from screenshot 15:09.
Ive added compilation scripts like you suggested but then i get other errors from screen shot 15:10 and still realvirtual bookmark/menu doesnt seem to pop up.
Afterwards i tried deleting folder Spacenavigator like its said here:
https://forum.realvirtual.io/knowledge-bases/2/articles/195-errors-concerning-spacenavigator-on-linux-and-mac
after that sometimes the menu pop ups but theres nothing beside login and download update, even after Im logged in. 
Im using Vulkan instead of OpenGL if thats some helpfull thread.
Cant wait for yours answer :DD Have a great day