Need Office 365 Accounts for Testing Purpose?

You can claim 25 testing accounts by joining the Microsoft 365 Developer Program.

https://developer.microsoft.com/en-us/microsoft-365/dev-program

You can use it for Boxer, ENS and Content Testing.

You can claim yourself a free domain if you want to use it with your Office 365 services.

https://www.myo365.site

Go to https://admin.microsoft.com to add your newly claimed domain.

This is a tutorial on how to claim a domain.

https://o365blog.com/post/my-o365-site/

A developer account also comes with Azure access https://portal.azure.com

There are other other trial features available available on Azure console.