Sure, Ubuntu is just another derivative of Debian

I would recommend Debian for Raspberry Pi.

I run a bunch of services off mine and it’s been rock solid, and I assume I get upstream security fixes quicker than I would if I were using one of the Debian derivatives.

Alternatively there is also GNU privacy assistant (GPA)

Hack within the terminal and Consolas for all my IDEs

Primarily cross platform websites and applications.

A great open source .NET project is Jellyfin.

Also, a fun fact is StackOverflow uses .NET :)

After having worked with python and JavaScript quite a bit, I enjoyed diving into the C#/.NET ecosystem.

If your goal is to make a career out of programming I would look at what languages are in demand in your region.

+1 for GNU Stow

I keep my dot files in git repo and have different branches for different machines/environments.

It works well, while not being over complicated.

Yes