What is the best way to automate a Windows desktop application in 2023?

I'm looking for tools, strategies, libraries, etc. that would be useful for automating arbitrary desktop applications. Ideally something free and open source. Robot Framework (https://robotframework.org/) looks promising, although the docs seem deliberately unclear about how useable the open source libraries are without the cloud SaaS being sold on top.

Does anyone have experience in this area? What's your secret sauce for robust desktop automations?