Consume PowerBI API (user owns data - no capacity) from Windows service

Question

We are a small/medium sized company that is looking to use the PowerBI API to extract paginated reports to PDF using a Windows service developed in-house using .NET 9. We do not want to purchase an embedded (capacity) license for PowerBI because it is more than twice the cost of giving each user a PowerBI Premium per-user license. We will also be embedding dashboards in a custom web application which we can do with the the per user licenses.

The issue is with consuming the API in the Windows service: Microsoft doesn't seem to provide a method of silently authenticating to PowerBI without using a capacity and service principal. We would like to be able create an Azure AD service account, assign it a license, and utilize that to authenticate the windows service calls to PowerBI. I've searched online and found some older examples using ADAL and a native app in Azure, but then replies were saying that method no longer works. Another talked about using a token store but seemed hacky.

Does anyone have any experience with this or can advise of a best practice? I hope that MS isn't preventing this type of authentication. What if a company only had 10 employees - can't expect them to buy a $60k / year capacity license

FYI We currently use SSRS to do this and it works seamlessly passing in secured user credentials but with it no longer being modernized and our company's need to migrate reporting to Power BI we need to move away from SSRS.

Thanks - any help is appreciated