Yeah I tried that. On KDE Neon there's no instant preview of what's getting printed in the system print dialog. Which means even more dead trees get wasted. Printing is a functionality that Mozilla has decided is unimportant so it's unlikely to ever improve.
It's an interesting attempt to replicate Vivaldi's functionality in a Firefox fork. Unfortunately it retains the horrible printing experience of Firefox.
I understand that HP is widely regarded as evil but my HP Officejet Pro 8500 does all of this on KDE Neon without even having to install a driver.