I have one of those X?1541 adapters from Ebay stuck on the printer port. This hooks to a real 1541.
I have the "older" cable type from 2006, and it worked fine only using StarCommander under DOS. I just ordered that newer one, as mentioned, for less than $20 shipped -- which has a simple jumper to make it work with either the older starcommander / cbm4linux or the newer OpenCBM software.
I got OpenCBM to compile and load on my Fedora 10 x86 system -- I am not certain how it will react to x86_64. But, it integrates nicely with Linux as a kernel driver, and I am waiting to try it out with any of my floppy drives (1541, 1571, 1581).
I left a post on SourceForge VICE regarding the use of 1581 mode on a Linux system. I was able to format & save from VICE to floppy using it in 1581 raw mode. However, that floppy won't directory / load on any real Commodore system with a real 1581 drive. Conversely, the same is true trying to read (or write) using an authentic 1581 floppy under VICE. Is this my unexpected use of the mode, or is this a flaw in my operation?