There are multiple ways to go about it, but the best and the easiest one is to use Unlit material shading mode, as @ClockworkOcean already suggested, then turning off the “Affect Distance Field Indirect Lighting” checkbox on the object:
But just keep in mind that the emissive material will still reflect in the specular component of the material (Lumen Reflections).
I agree that since UE5’s renderer is approaching realism of the offline renderers, we should get an ability to make lights with non zero area or volume actually visible to the camera. From physically based light transport perspective, it makes no sense to have a light source which illuminates the scene but you are not able to see it from the illuminated point.