Yes:
(1) using "sign for development only" does work,
(2) using "sign with my key" after using keytool is also fine. The keystore file (I am on OSX) is put at the top of your home directory (unless, I guess, you "cd" to some other location)
I know these are newbie questions and solutions, but they also prove that the sequence of steps to be followed is not so obvious.
My goal is to be able to write my own apps while remaining totally independent of Google and/or Apple. That seems impossible with Apple, and is probably going to be difficult with Google.
But thanks to JacobS, Jacque and others, I have now been able to install an apk without going through their store.
Apps from the store, including free ones, are very annoying: I just wrote a very simple Compass, because the ones I found on the store require all sorts of permissions that I am not willing to give (like access to my phone number). A compass needs absolutely NO permissions and any such app that does should by definition be suspect , whether it comes from the store or not!
For info, here is the code of Compass:
on openstack
mobileStartTrackingSensor "heading"
IndicateNorth
end openstack
command IndicateNorth
put round( mobileSensorReading("heading",false), 0) into lHDG
put lHDG into field "Heading"
put (lHDG+90)*pi/180 into lRadians
put 400 into x0; put 600 into y0; put 300 into NeedleLength
put round( (NeedleLength*cos(lRadians)+x0),0 ) &comma& round( (y0-NeedleLength*sin(lRadians)),0 ) &CR& x0 &comma& y0 into lPoints
set the points of graphic "Needle" to lPoints
send IndicateNorth to this stack in 200 milliseconds
end IndicateNorth
(that is for a Galaxy Note GN-T7000 which has a 800x1280 screen, hence the valuese of x0 and y0.)
VERY basic, I agree, but I don't need more than that and the security of knowing none of my private info is going anywhere.
Robert.