Take a look at IP cameras which support RTSP streams/onvif protocol. With that, you wouldn't need to use the manufacturer application or nvr. Will have to a bit of googling to find the ip : port and maybe password to those cams.
Synology and QNAP NAS have a surveillance plugin/addon to support such cameras. Although you might lose some features like PTZ, motion detection done via manufacturer software in cam/nvr(maybe the NAS plugins have figured out a work around, not sure).
Synology has a limitation of 2 cameras for free. More than 2 will need a paid addon. Not sure about QNAP.
But with wifi(and ethernet) cams, you might need a firewall or vlan setup so that they don't reach out to internet. Only allow RTSP ip : port from the camera into your network(probably isolate the whole nvr and camera system, no internet and can't reach other vlans).
If you can run virtual machines/dedicated hardware, checkout these software to run and record IP cameras. But will have do a bit of manual work.
Zoneminder
Shinobi
Blue Iris
MotionEyeOs
Another option is Ubiquiti's Unifi protect system. Not cheap, but works pretty good. Records offline, can view remotely too with ubiquiti account. They have had their fair share of issues(mandatory ubiquiti account to setup devices, bad updates, massive breach recently).
But locked down hardware. Think of them as apple of networking world.