Unfortunately, you have to have O365 installed and at this time, it has to be institutional O365, not an individual account. This is to do with how the licences are purchased, managed and distributed, all through the Microsoft Store for Education.
Sorry, but this is unlikely to change in the medium to long term future. There are many home educators who can't currently use MinecraftEE for this reason.
This forum is for Minecraft EDU, the now redundant version of Minecraft Education. For the latest discussion on MinecraftEE (Education Edition) please join our Discord.