  The 'Great Dimming' of the prototypical red supergiant Betelgeuse, which
occurred between December 2019 and April 2020, gives us unprecedented insight
into the processes occurring on the stellar surface and in the inner wind of
this type of star. In particular it may bring further understanding of their
dust nucleation and mass loss processes. Here, we present and analyse
VLTI/MATISSE observations in the N-band (8 - 13 $\mu$m) taken near the
brightness minimum in order to assess the status of the dusty circumstellar
environment. We explore the compatibility of a dust clump obscuring the star
with our mid-infrared interferometric observations using continuum 3D radiative
transfer modelling, and probe the effect of adding multiple clumps close to the
star on the observables. We also test the viability of a large cool spot on the
stellar surface without dust present in the ambient medium. Using the
visibility data, we derive a uniform disk diameter of 59.02 $\pm$ 0.64 mas in
the spectral range 8 to 8.75 $\mu$m. We find that both the dust clump and the
cool spot models are compatible with the data. Further to this, we note that
the extinction and emission of our localised dust clump in the line of sight of
the star, directly compensate each other making the clump undetectable in the
spectral energy distribution and visibilities. The lack of infrared brightening
during the 'Great Dimming' therefore does not exclude extinction due to a dust
clump as one of the possible mechanisms. The visibilities can be reproduced by
a spherical wind with dust condensing at 13 stellar radii and a dust mass-loss
rate of (2.1 - 4.9) $\times$ 10$^{-10}$ $\mathit{M}_{\odot} {\rm yr}^{-1}$,
however, in order to reproduce the complexity of the observed closure phases,
additional surface features or dust clumps would be needed.
