An updated post in the launcher thread led me to try Albert again. I had liked it when I first tried it, but it needed more development.
There has been a lot more development now, and the Github readme has also been updated to list the Ubuntu dependencies – most of these packages have very different Debian/Ubuntu names – so it’s easy to try the latest version instead of waiting for the Webupd8 PPA.
I have only used it for a few minutes, but I prefer it to Synapse, even when it is working. 