  A combination of searches for new heavy spin-1 resonances decaying into
different pairings of $W$, $Z$, or Higgs bosons, as well as directly into
leptons or quarks, is presented. The data sample used corresponds to 139
fb$^{-1}$ of proton-proton collisions at $\sqrt{s}$ = 13 TeV collected during
2015-2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses
selecting quark pairs ($qq$, $bb$, $t\bar{t}$, and $tb$) or third-generation
leptons ($\tau\nu$ and $\tau\tau$) are included in this kind of combination for
the first time. A simplified model predicting a spin-1 heavy vector-boson
triplet is used. Cross-section limits are set at the 95% confidence level and
are compared with predictions for the benchmark model. These limits are also
expressed in terms of constraints on couplings of the heavy vector-boson
triplet to quarks, leptons, and the Higgs boson. The complementarity of the
various analyses increases the sensitivity to new physics, and the resulting
constraints are stronger than those from any individual analysis considered.
The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a
weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up
to 1.5 TeV in the case of production via vector-boson fusion.
