Hello,
Here is the symptoms :

root@desktop:~# lpstat -p
printer deskjet-5600 disabled since mar. 04 août 2020 08:10:50 CEST -
    Backend /usr/lib/cups/backend/hp does not exist!

Resolution :
Installing " printer-driver-hpcups " (+ command " cupsenable deskjet-5600 ") wasn't enough, installing " hplip " seems necessary.

I don't know why it wasn't necessary on ascii.