Absent the ability to use a tripod, there are a couple of other approaches that should work.
1. Raise the ISO to the point where you can use an appropriate shutter speed for hand holding and enough aperture stop down for reasonable depth of field. Once home use one of the best noise reduction apps, such as Topaz Denoise AI, Topaz Photo AI or DXO.
2. For each scene, shoot a continuous burst using S-AF, using the best hand holding technique that you can manage. Again, use a higher ISO and moderate aperture for just enough DOF. All camera settings need to be on manual, no auto settings. You want to shoot a minimum of 8 frames in burst mode, and up to something like 32 at the top end. Even with good hand holding technique, the small movements will allow for a type of pixel shift, given suitable post processing. (Shaky Human Pixel Shift!).
Once home, you will need to use Photoshop to bring the frames in as layers. Then run Auto align. Then turn visibility on and off, one frame at a time, looking for frames that are obviously more shifted than most, deleting the most shifted ones. Next select all frames in the stack, and convert all to Smart Objects. This can take a while, depending on your file sizes and the speed of your computer. Go make a coffee.
Finally go to Smart Objects, and run the option to average the layers using Median mode. Apply the Median Stack mode (Layer → Smart Objects → Stack Mode → Median).
This will result in one image with substantially reduced noise and good clarity. This is because the image details are static, while the noise is random, and the averaging process removes anything that is not common between the frames.
I've run numerous trials on 2, and it has worked well, using both m43 and Sony FF cameras. If you shoot the burst, you can try either or both approaches (assuming access to Photoshop).
Here's an example in a Flickr album of 8 frames from an A7RIII, taken at ISO 6400, that I averaged as outlined above. No NR reduction was used in the processing. This was uploaded at almost full resolution, so be sure to view it full size in Flickr.
Brian