Can a landlord do general maintenance without alerting the tenants?
You mean in a common area, certainly. Things break and they need to be repaired. The building is owned by the landlord and generally landlords want to keep the building in good condition. Now if its something
like retile the entry way where you have to use the side door, painting a large area or any of that stuff they should give the tenants notice that it going to happen and the dates/time.
If you mean come in your apartment and fix your leaky faucet without talking to you about it first, then no. If you mean come into your apartment and fix your burst pipe thats flooding other parts of the building,
thats an emergency.