I got it to work. After hours of searching on the Net using multiple search engines, I never saw anyone explain how to make this work, so I invested some time, lots of wasted paper and no end of frustration until I got it. It appears to work as well with CUPS as it did on Windows.
I’m running Linux Mint 22 (Wilma) with KDE on top of it.
Set up the printer; you can find the user manual online. While cut-sheet/single sheet paper will work, it’s not reliable. The printer is too likely to eat the paper. It didn’t seem to like the front push or rear pull too much, either with CUPS. I’m using tractor-fed paper in the “rear push” configuration. The paper source is loaded from the rear of the printer, down under the main roller, around and back up under the ribbon guide. Notice what the Epson user manual says about making sure you simply lay the paper into the tractor feed and leave it with the top edge of the paper in the tractor. Don’t try to pre-load it. As soon as you turn the printer on, it will pull it forward until it senses the leading edge of the paper touching where the platten roller meets the one below it. Leave it like that.
Once you plug in the USB port, CUPS should notify you on the desktop of a new printer to configure. Choose the Epson brand, and then look for the 24-pin Generic driver. The LQ-590ii understands the basic Epson ESC/P2 commands just fine. Set the resolution to 360×180; it makes a difference how the generic Epson driver communicates with the printer. When it’s all configured, run a test page.
At this time, the paper should automatically advance to the proper place — ideally with the top edge even with the printer ribbon. It should print nice and clean, unless you need to make adjustments to the paper run. Mine feeds cleanly, but I took the time to site the paper supply inline with the tractor feed with no drag and no sharp bends.
The only thing I cannot figure out is how to access the built-in native printer fonts. They are really nice and clean and faster to print than the rasterized jobs from stuff like word processors. However, I cannot figure out the trick of how to format a plain text file with commands that include any font attributes. It seems none of the document software I am aware knows anything about native printer fonts.
I’ve found that printers are generally the worst to deal with, but the older the printer type, the easier it was to use.