It depends why people are talking over each other
You mention that the players are talking out of character.
If the chatter is, itself, not aimed toward moving the game forward (e.g., out of game jokes), then reminding people not to do that when you notice it happening can be effective. It's fine every now and then in a smaller group, but with enough people (8 is a bunch) it can very quickly bog down a session.
If the chatter is different people all trying to do actions simultaneously, players in my group have often used chat to "queue up" an action or to have an in-game conversation with another character. As long as the DM is following the chat, the action will happen eventually, with the DM switching between people every so often so no one is left out. Having a way to queue the action removes the need to constantly try to butt in.
If it's one person generally overpowering things, it might be worth either talking to that person about it (preferably 1:1 so they don't feel called out) or explicitly calling on people in turn to ask them what they want to do. You probably don't need a formal initiative system as long as you can keep track of it in your head. I haven't had this particular issue in any groups, so I'm speculating a bit with this last suggestion.