The main web backend is still ruby it seems: https://github.blog/2020-08-25-upgrading-github-to-ruby-2-7/ I can't remember where it was exactly but I remember recently stumbling on a random github-related OSS project that had chatter in the issues from githubbers talking about .NET and C#. It would not surprise me to see significant pressure from the now 2-year post-acquisition engineering org to get in line with the rest of MS's online services that are all .NET stack.

Microsoft does not have a consistent internal stack nor is anyone "encouraged" to use .NET. I don't know where this idea that Microsoft's online services all use .NET, for example, my team which delivers a large service as part of a top-level Azure offering is mostly all Go.

> I don't know where this idea that Microsoft's online services all use .NET

My only knowledge of this happening is when Microsoft took over Hotmail and replaced FreeBSD with Windows. I assumed like the other comments that it would be political suicide to continue to support a non-Microsoft stack

It's a massive company with a multi-decade history. There's probably some historical truth to it, but yea, it is not the current reality.

Ehh, I worked there on online services before Azure even existed and it would have been career suicide and an enormous legal fight to use anything outside MS's stack--IIS, MSSQL, COM & C++, then .NET. Hotmail got away with it for some years because they were an acquisition.

A lot has changed in the last decade

Why pick up a new gun you’re not used to, when you have a perfectly working footgun you know inside and out—even if it only allows you to shoot yourself in the foot?