I had an indication from Jasem that the PPA had resolved the issue (a day or so ago). When I use the ppa and install Kstars-bleeding I ended up with Kstars 3.5.4 Beta and my SX CCD still did not show up in the Indi Control Panel. So I was trying to find a way to get to 3.5.3 stable. I found this info on one of the download pages:

"If you would like to stop using Nightly PPA builds and instead return to using stable PPA builds then run the following commands:
sudo apt-get install ppa-purge
sudo ppa-purge ppa:mutlaqja/indinightly "

So I did that and I ended up with Kstars 3.5.3 Stable, but my SX CCD is still not connecting. However now I get a message from Indi(?) that the SX CCD is not connecting and I should check if it is connected and powered up. It is connected, it shows up in lsusb as the Starlight Express Lodestar and it runs fine in PHD2.

I seem to be making progress as at least now I get a warning about the SX CCD but I don't know how else to debug the connection to Kstars/EKOS

If I go to the Device Manager in Kstars and select the SX CCD and hit Run Service it says:
"Driver Indi_sx_ccd pid=2074 rfd=4 wfd=11 efd=12
Client 5: new arrival from - welcome!"

so somewhere it seems to be recognized, but not in Ekos?
the log does not tell me much more than it is not connecting.

Having run the ppa:purge above will I now only get 'stable' versions of Kstars rather than nightly builds? Yet installing kstars-bleeding seems to imply that you will get the latest (nightly) build. I have not tried it but can you just run:
sudo apt-get install kstars (instead of kstars bleeding)

Not sure any of this has to do with the SX CCD issue. It does seem that this update of release of 3.5.3 stable has a lot fewer issues than a few days ago. I am just trying to let the developers know that there are still some issues.