Hi @zuuks666,
- I’ve been there as well, but there is hardly any reason to switch off your computer like that. And apparently it includes system freezes. Please see [HowTo] reboot / turn off your frozen computer: REISUB/REISUO for more information.
- Kernel version 5.9 is EOL. I don’t know about the RT version, though. However, I highly doubt an RT version is necessary as I have a normal kernel version, always have, and virtualbox worked fine when I used it.
- More information will be needed if someone is to help, so please see How to provide good information