Yes, this is what I am doing now. But how these rpms will go into the final flashable zip?
(When I installed your 3.0.3.9 build I didn't need to install extra rpms.)

Plus what rpms should I install. There is one in the 'droid-local-repo/droid-camres' and there are 3 in the 'droid-local-repo/gst-droid'.
Are these 4 enough?

The other annoying thing is that I cannot access the real / because /android folder does not exist. Therefore I need to boot into android to be able to copy files from the pc to the phone, then I need to boot into a different sailfish rom and as root copy the files into this rom's home, then I can boot into this rom and can install the files from home.

Okay, I installed the droid-camres, gstreamer1.0-droid and gstreamer1.0-droid-tools rpms. Then I did 'droid-camres -w' and 'devel-su
mv jolla-camera-hw.txt /etc/dconf/db/vendor.d/
dconf update'
Now, the Mpx has values in the camera app in settings.
However the video recording still doesn't work.

Sensors:
This is again not clear in the hadk. :-(
It says there is a 'sensord-hybris.conf' file to hold the sensor configs.
And an example is available here
Yes, that file is in the '$ANDROID_ROOT/hybris/mw/sensorfw/config/' folder but its content as the same as in the example file.
Why do not the sensors work then?

One more thing. The hadk and the faq is referring to folders and files that do not exist in the sdk.
For example:
the hadk mentions: '$ANDROID_ROOT/hybris/droid-configs/sparse/etc/sensorfw/primaryuse.conf'

the hadk-faq mentions: '$ANDROID_ROOT/hybris/droid_configs/sparse/usr/share/csd/settings.d/hw-settings.ini'

In '$ANDROID_ROOT/hybris/droid_configs/sparse' there is no etc and usr folders. There is only one (var).
Should I create the missing ones and copy the files in there, then re-built the zip?

The sparse folder contains files you want to add to add to the image, like the config files from camres, sensor configs etc.

Why not use ssh to copy files to the phone? If you prefer a GUI you could use filezilla, scp would be your tool for the cli.

Thank you.
So this is a way to include some files into the build.
And how can I add rpms to install?

This is what I did. I copied them to the phone. But as I said I would like to include them into the build.

Filezilla doesn't connect. Coonect refused. Probably I need to enable the ftp connection on the phone. Do you know how? Thanks.

Have you enabled remote connection and set a password for nemo?
DDo you use port 22?