Hello again!
Indeed, Lumen and baked lights won’t work together, as Lumen’s dynamic system will clash with lightmass data, either bypassing it, or crashing the whole build.
If you need to use rect lights with Lumen, they must be set to “Movable”, then you just skip any baking. Lumen will read those lights, but they will behave more like point lights. You can play around with width and height values to improve the rectangle-like shape.