Installing LXD from APT installs it as a Snap package and while LXC programs are installed from a Debian package, running them tells me I need to install the LXD snap. Is there anyway to install LXC and LXD as a Debian package? Is LXD supposed to supersede LXC?
LXD is free/open-source software and is developed at linuxcontainers.org.
The maintainers have switched to producing only snap packages for LXD, for the following versions: LXD 2.x, 3.x, 4.x. You can see all these versions when you run
snap info lxd.
You can still use LXD 3.0.x as a deb package, which is supported by the LXD team until 2023. You get this version of LXD in Ubuntu 18.04. Note that LXD 3.0.x is feature-frozen (there are no new features but does get security updates).
Having said that, there is nothing that precludes a third-party (such as maintainers from a Linux distribution) to package LXD and distribute it in a different package format. You can get the freshest LXD in OpenSUSE, for example.
There used to be a difficulty in packaging LXD in Debian, because Debian has a policy to package separately each individual component packages (i.e. Go libraries in the case of LXD). And until some months ago, a few of those packages existed in a separate source tree (i.e. not a released upstream version). AFAIK, all these have been resolved now, therefore Debian may pick up again the task to package LXD. If you know an interested Debian Developer, you can ask them to look into this.