Ubuntu 20.04 - cannot print

Question

I use Ubuntu Mate 20.04, and just today I did an update. Not sure if it is because of that, but now I cannot print. I use an Epson Stylus SX115.

If I call system-config-printer, I get this state:

If I click on "Print test page" here, it works; if I click on "Print self-test page", it does not.

Now, I open a PDF document in the default PDF viewer on Mate, which is Atril Document Viewer. I choose File/Print there, I get this:

I have two entries from the printer, because troubleshooting earlier told me to enable some print server, but it makes no difference, both of them show the same problem.

I click on Print on this dialog, and I get this - "Print error" "There was a problem processing document ..." :

Unfortunately, there is no indication on what the error is - though just now I notice "0K" under Size ...

If I click Diagnose, I get to this:

... and then when I click Forward (for the second entry, which is what I've used so far):

I get:

There are status messages associated with this queue.

The printer's state message is: "Rendering completed".

Eh, great - this tells me nothing. If I click Forward here, I get option to Enable Debugging, where it gets stuck (and so I get repeated offers to Enable Debugging, even if I tried that several times before).

Obviously, at least some part of the printing works, since I can do "print test page" - but how can I get a PDF to print from the default PDF viewer?

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EDIT: If I do, from the command line (via Linux: How to print PDF files from the command line - makandra dev):

lp /path/to/file.pdf

... then Printing starts (and works) - but of course, I cannot change any print settings from a Print dialog.