Google and Connectwise offers free software for remote administration.
Google Remote Desktop: https://remotedesktop.google.com/
I previously wrote about MeshCentral, which currently does not support OSX, so we have to look around for other solutions, hence Google and ConnectWise.
Google looks pretty cool and has the potential to be the new goto, also the free version from Connectwise is a solution which just works and it has been tested in the wild by pros. I know of a few more solutions but they are not that polished as these free ones. The most important thing is that these are completely free to use and you do not have to pay anything for something that you not use that often and they are of course "secure" or as can be, as we all know that 99.9999% security is an illusion.
Tom from Lawrence Systems (US) has made a couple of introductions which you might find interesting.
Connectwise Control Free License for Remote Support
Free Remote Control With Chrome Remote Desktop 2020
List of Free Software and Services To Help Remote Working During Coronavirus Outbreak 2020
The last video is a compilation or summary from Tom, though not much new under the sun there. It is really an attempt to provide free services during these hard time we go through now, everything helps so to say, to stay home and isolate yourself from the damn Covid virus.
It is really not that difficult to do remote administration now-a-days, so there is no excuse that you cannot help your grandmother with her PC problems...while you can :)