To be fair in the UK Macs are absolutely dominant in this field.

Depends very much what you're doing; certainly not in my area (simulation software) at least, not for other than use as dumb terminals.

Yes, in Germany it's mostly Linux and Lenovo / Dell / HP desktops and business-type laptops. Some Macs, too.

I have no idea where in Germany you're based, or what industry you work in, but in the Berlin startup scene, there's absolutely a critical mass of development that has coalesced around macOS. It's a little bit less that way than in the US, but not much.

Berlin is very different from the rest of Germany.

This. According to my experience and validated by Germans and expats alike, Berlin is not Germany :)

In Norway where I live Macs are pretty dominating as well. Might be Germany is the outlier here ;-)

When I go to Ruby conferences, Java conferences, academic conferences, whatever, in Europe, everyone - almost literally everyone - is on a Macintosh, just as in the US.

Most people don’t go to conferences.

Ruby conference goers don't represent all the SW devs of Europe :)

Why do you think not?

And why not Java developers?

They seem pretty polar opposite in terms of culture, but all still turn up using a Macintosh.

Because every conference is its own bubble of enthusiasts and SW engineering is a lot more diverse than Ruby, from C++ kernel devs to Firmware C and ASM devs.

Even the famous FailOverflow said in one of his videos he only bought a Mac since he saw that at conferences everyone had Macs so he thought that must mean they're the best machines.

Anecdotally, I've interviewed at over 12 companies in my life and only one of those issues Mac to its employees the rest were windows/Linux.

True, but it is full of developers using Windows to deploy on Windows/Linux servers, with Java, .NET, Go, node, C++ and plenty of other OS agnostic runtimes.

Given the fact that the US has an overwhelming dominance in software development (including for the cloud) I think that the claim this is only a US phenomenon is somewhat moot. As a simple counter-point, the choice of development workstation in the UK seems to mirror my previous experience in the US (i.e. Macs at 50% or more.)

My experience in Germany and Austria mirrors GPs experience with windows/linux laptops being the majority and Mac being present in well funded hip startups.

Same in South Africa (50% mac, 30% windows, 20% ubuntu) and Australia.