SSIM Appliance upgrade

Greetings Group!  Happy New year!

I am seeking infomration on upgrade a 2 SIM Appliance environment running 4.7.4 to version 8.1

My questions is that while there is information on the migration process; is it possible to upgrade the OS of the appliance since the requirement for installing version 4.8.1 is to move to the latest OS version of Linux?

Thanks