So I have 5 ubuntu 20 nodes on a single network with sudo access. I want to spin up a private Ethereum network using nethermind client (not geth). How one may do such a thing - where to start is there a tutorial\dockerfiles that could help with such venture?
The Nevermind documentation is very well written, that's why I advise you to have a look at it: https://docs.nethermind.io/.
Regarding your request, it is possible to create a private blockchain using the Nethermind client on Ubuntu 20.04 servers. You'll first need to choose the consensus protocol that will be used for securing the network (either Clique or Spaceneth). Everything is explained in their documentation here: https://docs.nethermind.io/nethermind/ethereum-client/private-networks. They even created scripts to automate all the actions!