So, on the plus side with the new .net, I recently made a .net core web app on Linux, and generally it's been pretty easy. I'm also impressed at just how fast asp.net core is compared to asp.net, the time it takes to open your site in debug mode has dropped dramatically, from what used to be 1/2 minute in asp.net to a few seconds in .net core. On the bad side? Mainly the asp.net core team and their push for Dependenc…
As regards configuration, all the means you could want for configuration are there. You can access items directly [1], or via strongly typed objects. These all support multiple sources of configuration data, and many means of overriding them.
I generally really don't like environment variables as they expose configured secrets to everything in the same machine / container, but we make use of the standard configuration system's environment variable overrides, but we use akv2k8s.io and thus only expose secrets to the container's entry point application.
[1] public Startup(IConfiguration config) { // injects config store var setting = config["yourConfigKey"] // ... but you now have to convert this from a string for any other datatype }