I believe modern heat --> electric conversion systems use the turbine and several other additional heat --> electricity recapture systems to approach 50-60% efficiency at large scales so they can beat the Carnot Limit of just the turbine engine.
LFTR presentations said they could use the brayton cycle I think due to high temps, I'd imagine a fusion would also have the temps to enable brayton cycle and several other tricks to achieve good efficiency.
Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use.
https://www.powermag.com/efficiency-improvements-mark-advanc...
That claims 64% for a gas turbine.
LFTR presentations said they could use the brayton cycle I think due to high temps, I'd imagine a fusion would also have the temps to enable brayton cycle and several other tricks to achieve good efficiency.
Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use.