I installed snapd from apt and then did
sudo snap install snap-store. It seems like nothing happened to set up .desktop files for display in the lxpanel launcher.
I’m using vncserver (tigervncserver) instead of a login X environment.
I worked around the problem by modifying the systemd unit file for vncserver to include
Environment=XDG_DATA_DIRS=/var/lib/snapd/desktop, which causes icons to show up as expected after restarting the server.