Worthwhile to note that an alternative magnetic microscopy technique called MFM (Magnetic Force Microscopy) has been around for at least a few decades now, with resolutions down to 10 nm.
This new technique is done in a scanning electron microscope, which has some advantages - I’d expect you could get better temporal resolution since this scans an electron beam vs scanning a solid probe tip for magnetic force microscopy, and it would be easier to do multimodal analysis with other SEM techniques (standard SEM, energy dispersive spectroscopy for measuring composition, etc)
Edit: after skimming the paper, two interesting things stand out to me - it seems like the resolution is limited by the detector, maybe that can be systematically improved. And the lit review doesn’t actually discuss MFM, but does discuss electron holography (which I didn’t know about but is cool) and a couple other recent SEM based techniques that have more specialized hardware requirements
https://en.m.wikipedia.org/wiki/Magnetic_force_microscope