  We briefly review the status quo of research on the putative superconductor
Pb$_9$Cu(PO$_4$)$_6$O also known as LK-99. Further, we provide {\em ab initio}
derived tight-binding parameters for a two- and five-band model, and solve
these in dynamical-mean-field theory. The ratio interaction-to-bandwidth makes
LK-99 a Mott or charge transfer insulator. Electron or hole doping (which is
different from substituting Pb by Cu and thus differs from LK-99) is required
to make it metallic and potentially superconducting.
