arduino-1.8.4-linux32.tar.xz and ran
install.sh as outlined (the very sketchy instructions) in https://www.arduino.cc/en/Guide/Linux
This seemed to work OK, so I removed 354M of what I thought was the installer, only to discover that I had deleted arduino.
install.sh on closer inspection seemed only to create links into the uncompressed download in my home directory.
The whole process seems very un-Linux like; I had assumed that it would be installed in
/usr/share/ like most Linux programs.
I realise I could extract into
/usr/share/ and set permissions for other users, but surely there must be others who have wanted to do the same. The macOS version seems to have a proper installer; does one exist for Linux?