  Galaxy clusters are important probes for both cosmology and galaxy formation
physics. We test the cosmological, hydrodynamical FLAMINGO simulations by
comparing to observations of the gaseous properties of clusters measured from
X-ray observations. FLAMINGO contains unprecedented numbers of massive galaxy
groups ($>10^6$) and clusters ($>10^5$) and includes variations in both
cosmology and galaxy formation physics. We predict the evolution of cluster
scaling relations as well as radial profiles of the temperature, density,
pressure, entropy, and metallicity for different masses and redshifts. We show
that the differences between volume-, and X-ray-weighting of particles in the
simulations, and between cool-core non cool-core samples, are similar in size
as the differences between simulations for which the stellar and AGN feedback
has been calibrated to produce significantly different gas fractions. Compared
to thermally-driven AGN feedback, kinetic jet feedback calibrated to produce
the same gas fraction at $R_{\rm 500c}$ yields a hotter core with higher
entropies and lower densities, which translates into a smaller fraction of
cool-core clusters. Stronger feedback, calibrated to produce lower gas
fractions and hence lower gas densities, results in higher temperatures,
entropies, and metallicities, but lower pressures. The scaling relations and
thermodynamic profiles show almost no evolution with respect to self-similar
expectations, except for the metallicity decreasing with redshift. We find that
the temperature, density, pressure, and entropy profiles of clusters in the
fiducial FLAMINGO simulation are in excellent agreement with observations,
while the metallicities in the core are too high.
