Please give the latest version a try. I am not aware of any segfaults that have not been fixed upstream. Debian packages a really ancient version of cmus for some reason.
Thanks for the encouragement. Had a bit of fun getting it to build correctly[0], but got there in the end! Would love to create a new Deb package but haven't done it before, am short on time etc. - maybe another day.
For future reference: Always start with `apt-get build-dep packagename` Whenever you are trying to build a newer version of some software that debian also packages. There is no reason to start from zero and have to discover this information for yourself one build error at a time. If you want to see what the `build-dep` list is without actually running `build-dep` try `apt-cache showsrc packagename`
[0] - https://github.com/cmus/cmus/issues/347