It seems I mis-spake slightly the first time. When I try to install I get
The following packages have unmet dependencies:
nodered : Depends: npm (>= 5.8)
as did @Lupin_III but
apt policy npm
npm:
Installed: (none)
Candidate: 5.8.0+ds6-4
Version table:
5.8.0+ds6-4 500
500 http://raspbian.raspberrypi.org/raspbian buster/main armhf Packages
so that is a bit odd. I would have thought that 5.8.0+ds6-4 should be considered > 5.8