  We observed GRB190114C (redshift z = 0.4245), the first GRB ever detected at
TeV energies, at optical and near-infrared wavelengths with several
ground-based telescopes and the Hubble Space Telescope, with the primary goal
of studying its underlying supernova, SN2019jrj. The monitoring spanned the
time interval between 1.3 and 370 days after the burst, in the observer frame.
We find that the afterglow emission can be modelled with a forward shock
propagating in a uniform medium modified by time-variable extinction along the
line of sight. A jet break could be present after 7 rest-frame days, and
accordingly the maximum luminosity of the underlying SN ranges between that of
stripped-envelope corecollapse supernovae (SNe) of intermediate luminosity, and
that of the luminous GRB-associated SN2013dx. The observed spectral absorption
lines of SN2019jrj are not as broad as in classical GRB-SNe, and are rather
more similar to those of less-luminous core-collapse SNe. Taking the
broad-lined stripped-envelope core-collapse SN2004aw as an analogue, we
tentatively derive the basic physical properties of SN2019jrj. We discuss the
possibility that a fraction of the TeV emission of this source might have had a
hadronic origin and estimate the expected high-energy neutrino detection level
with IceCube.
