Is it possible to test out customized universal login page locally or on free tenant?

Hi I’m looking to customize my universal login screen following these directions:

However custom domains are only enabled in my production tenant. I’d prefer not to push out untested changes to production and wanted to know if it was possible to use my development tenant (which is on a free plan and doesn’t support custom domains) to try out these changes. Or is there another way I should go about testing these changes before uploading them to production? Thanks!

You should be able to customize your login/ sign-up page using the free tier account.
I think you will need to configure an email provider if you like to change Email templates.