Edit: …a decentralized Monero exchange

There’s the Monero shilling I expect in every comment

Some tangential preventative measures:

uBlock Origin on Firefox (and their browser of choice, if necessary). Preventing scam websites is a useful preventative measure that you don’t have to monitor.

Maybe have remote support software set up on their computers set up already. Something scammers don’t like to use.

Other thoughts:

I know this isn’t exactly what you’re asking, but if you can get your family/friends to know to never download a program or call a phone number… Or better yet, get them to simply reboot their computer, a lot of pain will be averted.

I wonder if there are ways you can manually lock down the computer that would also help.