Verified still present in Arch Linux HPLIP 3.11.7, HP Photosmart C4400 series PPD (along with many others).
Fix in above comment verified to work in Arch Linux.
Manually verified that HPLIP 3.11.10 still lacks the relevant ghostscript flags (-sstdout=%stderr, -sOutputFile=%stdout).
Verified still present in Arch Linux HPLIP 3.11.7, HP Photosmart C4400 series PPD (along with many others).
Fix in above comment verified to work in Arch Linux.
Manually verified that HPLIP 3.11.10 still lacks the relevant ghostscript flags (-sstdout=%stderr, -sOutputFile= %stdout) .