Specific games only, for example Rainbow Six: Siege didn't have cross play for an incredibly long time and during that time it was controller only for console users, so people starting using specialized hardware to connect a keyboard and mouse. That's what cheating is, Ubisoft threatened and DID ban a lot of these cheaters because it was specifically stated that using 3rd party hardware to change your method of input is cheating. However, if the game allows you to just plug and play with a keyboard and mouse without the use of any special equipment or software, then it's perfectly fine, there's no reason to call that cheating. In fact, I believe in some games you can control what inputs you are matched up against, I believe warzone had that feature.

So don't go calling people cheaters just for using features that are available to everyone including you, it's like playing call of duty then saying everyone using a different weapon then yours is a cheater.