  We present the discovery of a low-mass gas-rich low-surface brightness galaxy
in the Dorado Group, at a distance of 17.7 Mpc. Combining deep MeerKAT 21-cm
observations from the MeerKAT HI Observations of Nearby Galactic Objects:
Observing Southern Emitters (MHONGOOSE) survey with deep photometric images
from the VST Early-type Galaxy Survey (VEGAS) we find a stellar and neutral
atomic hydrogen (HI) gas mass of $M_\star = 2.23\times10^6$ M$_\odot$ and
$M_{\rm HI}=1.68\times10^6$ M$_\odot$, respectively. This low-surface
brightness galaxy is the lowest mass HI detection found in a group beyond the
Local Universe ($D\gtrsim 10$ Mpc). The dwarf galaxy has the typical overall
properties of gas-rich low surface brightness galaxies in the Local group, but
with some striking differences. Namely, the MHONGOOSE observations reveal a
very low column density ($\sim 10^{18-19}$ cm$^{-2}$) HI disk with asymmetrical
morphology possibly supported by rotation and higher velocity dispersion in the
centre. There, deep optical photometry and UV-observations suggest a recent
enhancement of the star formation. Found at galactocentric distances where in
the Local Group dwarf galaxies are depleted of cold gas (at $390$ projected-kpc
distance from the group centre), this galaxy is likely on its first orbit
within the Dorado group. We discuss the possible environmental effects that may
have caused the formation of the HI disk and the enhancement of star formation,
highlighting the short-lived phase (a few hundreds of Myr) of the gaseous disk,
before either SF or hydrodynamical forces will deplete the gas of the galaxy.
