Thanks for your response, I am unaware about anything related to Linux, however, I will look into what the terms you used mean.
I ended up giving them Chrome OS, which is amazingly fast compared to Windows as all operating systems should be (fast and environmentally friendly).
Chrome OS is perfectly compatible with their netbook, as all key binds were mapped perfectly, secure boot and other features provided by the OEM seemed to be operational and utilised by Chrome OS, although I have no idea how to tell.
Chrome OS is exceptionally simple, making it easy for them to use.
Since you can’t download apps on Chrome OS and all applications are sand boxed (where they can only access a few and only necessary permissions) it is hard (or impossible?) to get a virus.
uBO took care of phishing via content blocking, and it probably has other security features I have missed here.
I made the family member use Gmail (which also blocks phishing emails automatically) and changed most of their passwords for most of their online accounts, especially since they used the same, compromised (on the “deep web” [whatever this is, probably a fear mongering buzzword for encrypted Tor websites where the website owners are protected]) password everywhere.
I told them not to give their information online at all, except where entirely necessary, and to consult me for help with this.
Initially, they were enraged due to their age with this new change, and it took it’s emotional toll on me, but eventually they thanked me for making their computer a lot better.