There's not a lot you or any one individual can do, but every little bit contributes. Do measure expectations tho - in many cases (eg, Sony) the backlash is very much expected and they're just planning to weather it.
Biggest thing is to cancel your PSN sub (or other subscriptions relevant to whatever issue), stop buying buying games that fuel whatever practice (eg in the Sony case, stop buying digital games on Playstation).
Tell your friends and family why you're doing it, especially if there are people you play games with. Try to widen the impact from losing you, to losing your whole social circle. (Note that it probably won't work - people are set in their ways and not everyone cares about every issue-, and may not be worth it if you don't have another way to connect with them.)
Bluesky has some companies like Playstation and Xbox on it, so that's one place to be vocal. Twitter and Reddit probably still get read a lot by these companies too, so if you're on those, sure add to the dissent. They probably also value engagement on Facebook, maybe Threads/Instagram. Tho that makes me think, not sure if it's better to even add activity to their posts - maybe best way to send a message is simply to unsubscribe/unfollow? Sometimes it's worse to be ignored than hated.