@gcluley wild coincidence - looking for same, posed the question y’day in home automation village at #Saintcon. They said (ymmv):

Software:
Frigate (has object detection);
Blue Iris.

Cams:
Realink- can tap into vid signal;
Unifi may now, too.

Hubitat - widget linking home assistant to Google mini, approx $90.

I haven’t looked into these, so can’t recommend any, myself.