SharePoint Online Public Website to be discontinued.
Unfortunately, you can't create a public website within Office 365
Read more.
https://learn.microsoft.com/en-us/sharepoint/troubleshoot/sites/public-websites-be-discontinued
You can deploy a website to Azure with Azure App Service.
https://learn.microsoft.com/en-us/learn/paths/deploy-a-website-with-azure-app-service/