Altering the hosts file will just throw up HTTPS certificate errors. Showing a “you are being hacked” page every time he goes to visit his favourite propaganda websites would probably only make things worse.
OP was not very specific about what behavior they actually wanted. Changing the host file would prevent the uncle from visiting those sites, but as you say, it would not be subtle.
Altering the hosts file will just throw up HTTPS certificate errors. Showing a “you are being hacked” page every time he goes to visit his favourite propaganda websites would probably only make things worse.
If you alter it to 0.0.0.0 then it shouldn’t pop an SSL error, it would be a connection failed error.
OP was not very specific about what behavior they actually wanted. Changing the host file would prevent the uncle from visiting those sites, but as you say, it would not be subtle.