Thanks for the links!
Unfortunately, setting those values (StochasticInterpolation, and the ones in the video) didn’t help. I think those were intended for grainy/noisy shadows - mine weren’t.
I did notice that I didn’t get the flickering effect unless my emissive mesh was practically on the surface of another non-emissive mesh (see here: UE5 - Flickering from emissive mesh under another mesh - YouTube I tried a point light first and it looked fine, then I tried an emissive cube, which also looked fine. Then it started going bad when I lowered the cube down the mesh of the road). Is this expected?