Put the cameras on their own VLAN with no internet access. My Hikvisions are scraped by Zoneminder. Home Assistant completes the setup, behind HA Proxy for a bit more protection.

My setup is perhaps a bit gilt edged but then I am a sysadmin and networks bod and PHB all in one odd package! Home IT needs to step up its game. If you get done over then the cost can be very high. I don't think it is sufficient to simply use your ISP provided router, plug in a few IoT thingies and download a few phone apps and stick your fingers in your ears and chant la-la-la.

I would hope that most of the inhabitants of this parish are capable of putting together a reasonably safe setup and also look after their less technical friends and family (it can be a thankless task but a I think it is a duty.)

Don't forget that your attic, garage or cellar may make good places to keep IT gear in but do consider heat, cold, dust and fire risks.