I see Docker / your container tech of choice as a solution to this. Your server can still run whatever distro, and a specific app can run a different one.

This can be annoying from the sysadmin perspective, since there are now multiple operating systems to take care of, but at the same time, the developer may not be able to produce builds for all distros their users would like.

Ubuntu is a fine choice IMHO, given the above. But yeah, some debs / ppa would be nice.