Establish a specific trusted channel of communication and a backup. Anything important must come through those instead of just any random source. Educate them on scams in general and if they aren’t on social media already, keep them away from it.

Especially if cognitive decline hasn’t set in yet, also encourage them to make healthier lifestyle choices, take preventative measures, get checked up, and perhaps even get hearing aids to keep their minds sharp for some more years.

I’ve personally provided them a locked-down device that only connects to my aforementioned trusted communication channels.