I find that I cannot print an email attachment; when I try I get the message that “the printer is not available or is setup improperly”. But if I save that same attachment as a pdf, it will print just fine. I mention this in hopes it may shed some light on your printing issue.
Chromium browsers on Endless OS may print garbled text with new HP printers due to driver or compatibility issues. Try updating printer drivers, using a different browser, or printing as PDF first.
I see the same thing with my HP printer sometimes, and I’m afraid I don’t know why. You may have better luck using printing to PDF and then printing the resulting PDF.
Chromium browsers on the Endless OS may print best gibberish with new HP printers try updating the printer drivers and using a different could browser.