For me they are the most obvious when the same account posts the same thing over and over and never anything else. They are typically overly generic.
There is also a trend where someone new will follow you and then immediately comment something overly generic on a post. The latest one that I’ve seen several times is “great portfolio, keep it up.” When three different new accounts follow you and say that it stinks of automation.
The automation tools allow you to set up searches based on likes, keywords and other things and put in a handful of generic comments that they can then randomize and post for you.
Hope this helps.