That printer was released in 2018, 2 years after 14.2 was released, so it's likely that the HP drivers in 14.2 don't have full support for this printer.
You could try and build hplip using the source/SlackBuild from -current. Do make sure you have
python3 installed as it's required.
Code:
wget -r -nH --no-parent --reject="index.htm*" --cut-dirs=4 https://mirror.slackbuilds.org/slackware/slackware64-current/source/ap/hplip/
cd hplip
sh hplip.SlackBuild
upgradepkg /tmp/hplip-*.txz