But we wouldn’t be able to detect human level lunar activity in a million years time.

We can barely detect human activity from 50 years ago when we know exactly where it is.

I think we are More likely to spot ancient Geostationary satellites, which will have drifted away from a perfect circle but should still be noticeable. LAGEOS aren’t in anywhere near that high an orbit but should survive 8 million years. They have a plaque on them designed by Sagan should a future civilisation find them.