> The cupsctl command should show "_debug_logging=1". Before, I used cupsctl --debug-logging which returned no errors - now I retried with cupsctl LogLevel=debug1 and this finally gives an error_log:
E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-310sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216xcms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-500cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-1200x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-500cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-620sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-1200x1200cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-6220sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-510cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-1200x1200cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3170sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-1200x1200cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-1200x1200cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-310-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-1200x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-1200x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-510cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-1200x1200cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3170cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-1200x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-660sc.cts\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-310cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216xcms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-1200x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600-1200x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-1200x1200cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3170-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3170-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-1200x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-1200x1200cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3160-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-310-600x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-1200x1200cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-1200x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-1200x1200cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-610-1200x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-216x-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLX-3170cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-1200x1200cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-1200x600cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-300-600x600cms2\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Bad driver information file \"/usr/share/cups/model/samsung/cms/CLP-310cms\"! E [08/Jan/2018:14:31:48 +0100] [cups-driverd] Skipping \"/usr/share/ppd/samsung\": loop detected!