This is something the rightwing repeat over and over again and is simply not true. For example here's a member of the ANC government condemning farm attacks:
Link:
Our current president himself responded to a protest about farm murders in 2017:
Link: https://ewn.co.za/2017/11/01/ramaphosa-calls-for-end-to-farm-killings-condemns-flying-of-old-sa-flag
Not something he would do if he was behind it or keeping it a secret as people have been saying on twitter... But right wingers keep saying the ANC denies farm murders exist - all day long:
Here's a another ANC member condemning farm attacks (2020):
^Here's another instance - ANC Condemns farm murders. Here was even an official statement on the governments website:
There are many more examples. The allegation that the government denies farm attacks exist is imply untrue.