  We reanalyse the ratio $\varepsilon'/\varepsilon$ in the Standard Model (SM)
using most recent hadronic matrix elements from the RBC-UKQCD collaboration in
combination with most important NNLO QCD corrections to electroweak penguin
contributions and the isospin-breaking corrections. We illustrate the
importance of the latter by using their latest estimate from chiral
perturbation theory (ChPT) based on the $octet$ approximation for lowest-lying
mesons and a very recent estimate in the $nonet$ scheme that takes into account
the contribution of $\eta_0$. We find
$(\varepsilon'/\varepsilon)^{(8)}_\text{SM} = (17.4 \pm 6.1) \times 10^{-4}$
and $(\varepsilon'/\varepsilon)^{(9)}_\text{SM} = (13.9 \pm 5.2) \times
10^{-4}$, respectively. Despite a very good agreement with the measured value
$(\varepsilon'/\varepsilon)_\text{exp} = (16.6 \pm 2.3) \times 10^{-4}$, the
large error in $(\varepsilon'/\varepsilon)_\text{SM}$ still leaves room for
significant new physics (BSM) contributions to this ratio. We update the 2018
master formula for $(\varepsilon'/\varepsilon)_\text{BSM}$ valid in any
extension beyond the SM without additional light degrees of freedom. We provide
new values of the penguin parameters $B_6^{(1/2)}(\mu)$ and $B_8^{(3/2)}(\mu)$
at the $\mu$-scales used by the RBC-UKQCD collaboration and at lower scales
$\mathcal{O}(1\,\text{GeV})$ used by ChPT and DQCD. We present semi-analytic
formulae for $(\varepsilon'/\varepsilon)_\text{SM}$ in terms of these
parameters and $\hat{\Omega}_\text{eff}$ that summarizes isospin-breaking
corrections to this ratio. We stress the importance of lattice calculations of
the $\mathcal{O}(\alpha_\text{em})$ contributions to the hadronic matrix
elements necessary for the removal of renormalization scheme dependence at
$\mathcal{O}(\alpha_\text{em})$ in the present analyses of
$\varepsilon'/\varepsilon$.
