2: You could easily compile Samba yourself for FreeBSD in the past, last time I tried a new version it broke in what I remember being due to linux-isms (yes there is ports, but being reliant on older versions if ports maintainers can't keep up isn't a good thing).

3: The only "fairly basic" stuff that's hugely different is mostly the absence/reliance on shell-scripts (when building), but that has little to do with the actual code function (Personally I often used Node scripts in those scenarios, Python scripts would probably be an improvement since there's no reason it couldn't be everywhere).

I used to use Tremor to decode Ogg audio (no UI needs, just binary data in, arrays of primitive values in audio buffers out), early versions were easy to compile under Windows but building later versions were buried in shell scripts generating headers,etc for no real good reason (maybe to help port when working on a Linux workstation to other embedded devices but made the code less easily compilable by default), the core functionality only really needed a C compiler as early versions showed.

I can agree that something with advanced UI's like Blender (that relies on GL/3d rendering for UI) might not be easily portable, but when algortihm libraries often requires heavy reworking it's not a good thing (Here I think Github has helped since people has had an easier time to contribute, it's a sad thing that people are moving away due to the AI-crap).

In the end, it's not about _actual_ differences but more of a superiority complex of Linux users that is the main roadblock.