What you are looking for is a bit of a hard ask, as most security cameras do not save to a network-attached USB drive, and anything that can would require a lot of configuration and in turn, would turn your router into a workhorse for saving the CCTV streams.
Along with requesting these devices are secure but do not require an app to configure. Anything with a Web Gui backend and not an app I can almost guarantee is made in China and not worth the time to get configured. I will outline what your best solution will be below.
1. A cheap Blu Android phone, only to be used with Wi-Fi and configuring your devices. – https://amzn.to/40zHHpa
2. Riolink DVR, capable of recording up to 8 camera streams, this kit comes with 4 cameras to get you started. – https://amzn.to/3QYnwxW
3. TP-Link Deco – TP-Link Deco AXE5400 Tri-Band 6E Mesh System – Wi-Fi up to 7200 Sq. Ft. – https://amzn.to/3FYPNys
The Riolink DVR will be attached to your home network via
an ethernet cable, Riolink does not require a subscription
when using a Network DVR