I know FR24 has its limitations but I use it as a situational awareness aid and it is effectively ADSB IN if you are in a mobile coverage area. It’s also displayed on Avplan (but not on OzRunways I believe). However, eyes out of the window is my best defence. Just a few hours ago a foreign student in an FTA Diamond made a very poor departure call while I was flying in the vicinity. It was visible on FR24 and that greatly assisted in spotting it visually.