I am using a network based Dahua branded system, nothing big only support 4 cameras, which should also be enough for most people i would think.
My friend run a Hikvision system, it have also performed just fine aside for a cable " dying " now and then due to exposure and mice / rats on his " farm "
You of course can set up remote viewing and get notifications on a smartphone ASO, or log in via a PC, i like the PC route as i always sit in front of it anyway, and it is plenty powerful to run that in one window while i do anything else.
I have a tablet on my bedside table that also get notifications when something human or vehicle shaped are near my car ( filmed from above so nothing in the background to give false alerts )
There are also a ton of small home CCTV systems these days, but i dont really keep up with these today.