Restore RouterOS

Hello, I have a Routerboard 750 GL that is running OpenWRT and I would like to install RouterOS back. How is that possible? Is there a license I should have backed up? Thanks!

You won’t find that information here. You will need to look at the OpenWRT documents to find how to restore the original RouterOS.
But I would suspect that you will need to use the MikroTik Netinstall utility.

There is already such discussion with some usable hints. Find it…