I have also installed the plugins (for hplip-3.5.11). Nothing works with a GUI. I tried from a terminal, and when it stopped I copied all the plugins in a subdirectory of ~/.hplip/ (I don't remember which) to a the directory firmware/ created in /usr/share/hplip/data/ . I had then to create the file /var/lib/hp/hplip.state containing
I have also installed the plugins (for hplip-3.5.11). Nothing works with a GUI. I tried from a terminal, and when it stopped I copied all the plugins in a subdirectory of ~/.hplip/ (I don't remember which) to a the directory firmware/ created in /usr/share/ hplip/data/ . I had then to create the file /var/lib/ hp/hplip. state containing
[plugin]
installed = 1
eula = 1
version = 3.15.11
And it worked.