Hi, I have an old HP Laserjet. For HPLIP installation, follow the instruction on this page:
https://developers.hp.com/hp-linux-imaging-and-printing/install/install/index?language=en
(you need to run it in terminal, there is no GUI)
HPLIP can be download here:
https://developers.hp.com/hp-linux-imaging-and-printing/gethplip
(select Ubuntu as OS in drop down list)