There is no pre-existing EF-MD adapter that I am aware of. The Flange Focal Distance (FFD) of MD mount is 43.5mm, while the FFD of EF mount is 44mm. That's only 0.5mm for an adapter without optics. For a hypothetical adapter with optics, you'd likely be multiplying focal length by 1.4x, so 85mm → 128mm.
There is no pre-existing EF-M42 adapter that I'm aware of. The FFD of EF is 44mm. The FFD of M42 is 45.46mm. There is -1.45mm of space in which to place an adapter, and the EF mount is too large to sink into an M42 mount.
The feasibility of modifying the lens depends on its specific construction and design. Although there is no aperture or autofocus mechanism to complicate conversion, I personally would not try, unless the lens was particularly cheap, like less than $10.
Converting to M42 is not as simple as just cutting threads into the existing EF mount because the FFD of M42 is 45.46mm. Ordinarily you would need to shorten the lens by 1.46mm. Given the apparent design of the mount portion of the adapter, based on examination of the photograph in your question, it would not be possible to just shave the barrel down. However, since the lens is available in Nikon F mount, the built-in focusing mechanism probably has enough "play" to allow infinity focus after altering the mount.
Another option is to cut off the threads and drill screw holes into a thin lens reversal adapter for MD mount. (Search for "Minolta MD reverse ring". Look at the pictures to find the thinnest one available.) Since the FFD of MD and EF are similar, the lens would likely still focus to infinity, though it might lose some close focus.
I would opt for a different lens. Other lenses known for producing swirly bokeh include those in the Helios series. I have also encountered lenses that produce mild swirly bokeh that is most noticeable with foliage in the background. You may even already have one without having previously noticed the swirl.
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