"How would you do {night, portrait} mode on a real camera" has been brought up a few times in this post and the answer is: you don't, because it's not needed. I can prop an iPhone on the windowsill and let it do a 30 second night mode capture, and I can also prop my Nikon Z7 on the same windowsill and let it do a 2-5 second exposure. The latter is so much higher quality it's no comparison at all. (And 2s can be hand-held at 24 mm, unlike the 30s night mode)

Though of course deep sky photographers do actually just this - many exposures composited together - but then we are talking about subjects so dim you need effective exposures of 30 minutes or so.