I just upgraded to Kubuntu 18.04 to 18.10 on my AMD64 desktop and found that asi-common is not available from stable ppa. Thus indi-asi can't be installed.
I am also using Kubuntu 18.10. As far I can see there's no version built for 18.10. At least I can't find it on ppa repository. Yet!
You can install the 18.04 version. Here: launchpad.net/~mutlaqja/+archive/ubuntu/...buntu18.04.1_all.deb
And wait for the 18.10 version and then upgrade.
That solved my problem.
Install with:
sudo dpkg -i asi-common_0.8.0+r3846~201803271859~ubuntu18.04.1_all.deb
After that you can install indi-asi normally.