  Solar flare ribbons are intense brightenings of principally chromospheric
material that are responsible for a large fraction of the chromospheric
emission in solar and stellar flares. We present an on-disc observation of
flare ribbon substructures in an X9.3-class flare observed by the Swedish 1-m
Solar Telescope. We identify categories of ribbon substructures seen in the Ca
II 8542 \AA, H$\alpha$, and Ca II K lines, focusing on their spatial locations
and their (spectro-)polarimetric properties. Color Collapsed Plotting
(COCOPLOT) software is used to assist in identifying areas of interest. We
present five categories of spectral profiles within the general body of the
flare ribbon: (1) Extremely broadened spectral line profiles, where the
standard Fabry-Perot interferometer wavelength windows ($\approx 70$ km
s$^{-1}$) are insufficiently wide to allow for a complete analysis of the
dynamics and atmospheric conditions. The mechanisms causing this degree of this
broadening are not yet clearly understood. (2) Long-lived, dense kernels that
manifest as more saturated chromospheric line profiles with lower signal in
both Stokes parameters. They are interpreted as footpoints of bunched magnetic
field loops, whose chromospheric lines form at greater heights than the nearby
areas. (3) Doppler-shifted leading edges of the flare ribbon in regions that
transiently display lower Stokes signals due to the emission dominating at
greater heights in the atmosphere. (4) Condensed coronal rain overlapping the
flare ribbons in the line of sight, producing exceptionally high Doppler shifts
near the footpoints...
