I see that I had to execute ./nodebb build in the container. I am guessing that it is because after removing the container, the build directory was gone and needed to be rebuilt, which tells me I have to put a build command on every container startup. This is not very optimal. I am hoping at some point in the future we can have a more hands-off docker-friendly deployment (like with env vars and all).
pkg install -y pkgconf vips
cd /usr/ports/graphics/vips/ && make install clean
I had to add DISABLE_VULNERABILITIES=yes to the end of the last command, because of some outdated dependency in the port. AFAIK the vips package is only used during installation or upgrade of NodeBB, so that shouldn't be any security issue.