Since the 5.10.2-164 is not solving my issues, I need a working system. Is there any possibility to uninstall the 5.10 kernel without messing up the system and any dependencies? VirtualBox does actually not work because of installed 5.10 kernel and booted 5.6 kernel. I hope, with uninstalling the 5.10 kernel VirtualBox is running again.
BTW:
sudo clr-boot-manager set-kernel com.solus-project.current.5.6.19-159
is on my system not reboot persistent. Also i have changed the default kernel in GRUB with "d", which is also not reboot persistent.