My result from the new lighting course. Tried to get good results using only an HDRi.
Whoa, that's a long render time! Is the Device in the render properties set to GPU Compute?
There shouldn't be any splotchiness - if you're using the denoising option in the View Layer properties, turn that off and try using the denoising node in the compositing workspace instead. It should already be set up for you in the file, but you can check just in case.
I'd also recommend increasing the number of diffuse bounces to 4 or more - the limited GI preset only gives you 1 and that's just not enough for an indoor scene.
jlampel This took almost 4 hours to render on a RTX 2070 super, with the presets "Final" and "Limited Global Illumination" with 500 samples.
Is there anything else I can do to reduce the splotchyness, or render time?