Hi,
Would it be correct to assume that this is an ML-1865 without a W suffix (that is, not the ML-1865W which has AirPrint support)?
If so, a discussion Samsung ML-1860 and latest MacOS could possibly be of interest. The workaround (for
another model) described by Matti Haveri is intended to eliminate a problem with a downloaded package not opening/installing under the latest operating system versions. Perhaps worth a try. Under Samsung Printer Drivers v2.6 for OS X, the article Printer and scanner drivers for Mac - Apple Support lists a Samsung ML-1860 Series version 1.03.02 driver. This would be experimental. It may or may not work.
Before testing anything, make sure that you have backup copies of all important files. Software conflicts cannot be ruled out.
You may have to reset the printing system between tests. See the following articles for details:
Reset the printing system on your Mac to solve a problem – Apple Support (UK)
Add a printer to your printer list so you can use it on Mac – Apple Support (UK)