UNIX Webservice technology options?

I need to create a simple WebAPI which will have access to a database of thousands of users/contacts with the normal information, FirstName, LastName, Street1, Street2...

each with a unique Integer ID.

And I need a WebAPI which accepts one parameter, the Unique ID, and return the required information.

I have a WordPress site, but do not think this is something WP is set up for. Or is it?

What is the range of choices for this?

I consider C#.NET to be a non-starter, due to the need for a Windows license.

What other C# options are there?

.NET CORE??

That would interest me, actually, since I have as yet had no experience with .NET CORE.

I could also choose Node.js.

What other choices can you suggest?

What do you consider the best choice?

Thanks.