It barely has a plot. New characters and new Miraculous related things are introduced once in a blue moon but by and large it's just Hawkmoth makes a monster of the day, LB and CN beat it, back to status quo.
Like mid season 2 they start to add new heros but they very rarely show up. Season 2's finale adds a new antagonist to assist Hawkmoth but halfway through season 3 she's shown up a grand total of once since.
So not much out a plot. Though very very rarely they'll suddenly make a callback to a random episode 2 seasons prior.