It's a standard full sized external Mac keyboard for Norway bought directly from the Apple store. We share the keyboard with Denmark too I think. The Swedes and Finns have different keyboards, but I think they use a similar combination for backslash.
So the Mac issue applies to 4 countries in the Nordics at least. Please note that traditional PC keyboards use a different layout for some characters and may in some cases have a dedicated key for backslash too, in case you Google Norwegian keyboards. It's one of those Mac vs PC things we are used to.
Before anyone starts suggesting connecting a PC keyboard to my MacBook Pro, keep in mind that I use the built in keyboard almost 50% of the time and having two different key mappings is a hassle
Regarding backslashes and other special characters,
I never said it's on Java specifically, but the US centric culture in general. K&R used curly brackets when they designed C because they fit the US teletype character set of the 60s/70s, but that doesn't mean it's the best choice today.
I'm not suggesting we use special unicode symbols like arrows and emojis, but just pause for a minute and look beyond the US keyboard and see if we can find a solution that also works ergonomically for at least some non-US countries.