Any Suggestions For A Free Customer-facing Web Application That I Could Use To Simulate A Business Environment To Practice Sysadmin And Iam Concepts?

I've got a good amount of experience working in a large decentralized corporate environment, and my background is in Cybersecurity. However, I'm looking to try to simulate an environment of say, a small business that provides some sort of service to customers where they login to a web portal via a web application. Kind of like a 'pretend business' without actually being one. I'm familiar with vulnerable web apps for pen testing and was wondering if there's any free ones that could do the same for SysAdmin concepts? It could be a real web application that provides any sort of business service, the problem is that mostly these web apps are either developed internally by customers, or cost a good amount to purchase a license for a vendor (and may not be on-prem to boot).

Just looking for a web app lets me create a lab environment where I can practice concepts that are customer facing like:

- Customer registers and creates a username/password for the web app that is then stored

- Possible integration with identity providers like Okta to test out

- Backend integration with Active Directory where an internal employee can create privileged rights for roles inside the web app (lets say, customer support needing access to some dashboard inside the app that customers don't have access to)

- Other typical things like using IIS, setting up certs, DNS, etc, etc ..

Might be a tough ask if there's anything like this that is free or trial license, and maybe an even bigger ask if its preferably open source (and installable on Windows Server.)

If anyone has any ideas of an ideal app like this, or even tutorials where some wise content on Youtube or sites like Udemy go through such a scenario like this it would be greatly appreciated.