Hello, jtollet.
Thanks for your solution. But unfortunately it doesn't work for me. And I try to figure out what's going wrong. First, when I follow /etc/cups/ppd/.. I see, that there are 2 files there: RICOH_SP_150SU.ppd and RICOH_SP_150SU.ppd.O with the same data. So I tried to rename
*cupsFilter: "application/vnd.cups-raster 0 RICOH_SP_150SUFilter.app
into
*cupsFilter: "application/vnd.cups-raster 0 RICOH_SP_150SUFilter
on both of them. When I follow /usr/libexec/cups/filter/... I see RICOH_SP_150SUFilter file, already without .app. But when I try to print something, I get an error: "Software for the printer is missing. Contact the manufacturer for the latest compatible software." Are there any ideas, what's the problem? Thanks in advance.