I recently fixed another issue on my Librem 15v3 which I will post here for the sake of recording these solutions.
I managed to get my librem to connect to my HP 3510 Deskjet WiFi printer.
To do this I had to use the hp-setup configuration tool that comes pre-installed with PureOS.
However, this is a CLI tool that needs to run in its UI form to enable Wifi setup, by default the CLI options only give you usb/net/parallel port.
To run hp-setup in UI mode, you need to ensure that you have hplip-gui installed,
sudo apt install hplip-gui
connect the laptop to the printer using the usb cable the, and run the hp-setup from your xterm window and now you will see the wifi optoin, select it and follow the wizard instructions. You will be required to select your network wifi (the one you connect to normally, not the printer’s wifi) and finally the printer will connect to the network.
Note, when you click ‘Next’ or Continue on the wizard, there is no indication that anything is happening and it takes 30 sec or so before the setup completes and moves to the next step,
Finally when the setup is complete, just close / cancel the hp-setup tool and you will be required to run it once more with the printer IP. Check which IP was allocated to your printer (on the printer screen press the wifi button to see the IP) and run the command again,
hp-setup <the IP address>
this will now re-open the hp-setup tool but this time it will allow you to set up a new printer queue on your machine which will be accessible to any of your print command UIs.