SANE has had backends for some of the X11xx series of Lexmark scanners. They don't work with the X12xx series, which is what I have. I tried everything I could think of to fool it, but no go.
If you find a magic solution, do tell us.
I'm thinking of donating that Lexmark all-in-one to a recycling place after I use up the cartridges. It was basically free when I got it but it's pretty thirsty for ink and is not economical to run. The cartridges are expensive. It doesn't do a great job of printing, can't be made to scan in Linux, and can't be used as a standalone copier. It requires software in order to work as a copier and the software is Windows-only. I hate to foist it on someone else, but I guess if it was cheap enough it might be better than nothing for a Windows user.
I have a good but ancient SCSI scanner attached to that computer, so I really don't need another scanner. I also have a laser printer and two other decent color printers (one on a print server), so I don't need the printer part either. My other desktop is attached to a Canon all-in-one that was free after rebate when I bought a laptop in August, 2007. The Canon has decent Linux support for printing and Canon has a Linux scanner driver that works both standalone and with the Gimp. Also, copying with the Canon is independent of any operating system and works even if the computer is turned off.