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.

I use Bitdefender, and it's great.

One tool I install on every computer I work on is Unchecky. It automatically unchecks all of the "install bullshit Spyware" boxes when installing programs.

But, really the best option is to make them a user account that can't install software. Windows Defender is actually pretty good if the user doesn't have admin privileges.

Bitdefender and Malwarebytes, both in the free version.

Note that you'll have to install Bitdefender first, they detect the installation of Malwarebytes and request it to be removed first, which is shitty, since that's a totally different use case - and they don't interfere with one another at all.