@chris36 I'm hoping this might help somehow. You mentioned that you have installed 20.04 LTS but you didn't specifically say that it is Ubuntu MATE that you are using. Since this is the Ubuntu MATE forum, I will assume that it is indeed Ubuntu MATE that you are using. When I install the distribution, I make use of the Ubuntu MATE Welcome app to install the things I know I will need (codecs, drivers, etc.) and I install HPLIP from there. I have yet to have any trouble with it missing components or not working.
If you are interested in trying that, in the off-chance that it's using some tweaked version or installer that is not used by Ubuntu or other derivatives, this is what I do:
Ubuntu MATE Welcome > Getting Started > Drivers > Printers > Click the Install button next to "HP Linux Printing and Imaging System"