  We study weak gravitational lensing convergence maps produced from the
MillenniumTNG (MTNG) simulations by direct projection of the mass distribution
on the past backwards lightcone of a fiducial observer. We explore the lensing
maps over a large dynamic range in simulation mass and angular resolution,
allowing us to establish a clear assessment of numerical convergence. By
comparing full physics hydrodynamical simulations with corresponding
dark-matter-only runs we quantify the impact of baryonic physics on the most
important weak lensing statistics. Likewise, we predict the impact of massive
neutrinos reliably far into the non-linear regime. We also demonstrate that the
"fixed & paired" variance suppression technique increases the statistical
robustness of the simulation predictions on large scales not only for time
slices but also for continuously output lightcone data. We find that both
baryonic and neutrino effects substantially impact weak lensing shear
measurements, with the latter dominating over the former on large angular
scales. Thus, both effects must explicitly be included to obtain sufficiently
accurate predictions for stage IV lensing surveys. Reassuringly, our results
agree accurately with other simulation results where available, supporting the
promise of simulation modelling for precision cosmology far into the non-linear
regime.
