I have two sons. Big on gaming, youngest plays for his uni in esports. So it has never stopped. How I dealt with it. After school there is a schedule, get changed, get food and a drink and a chat about your day, specifically what did you study in each subject, this can also spark conversations about it too. At a set time they start their homework and I was there to guide, suggest, whatever. At a certain time they were allowed tech but only if they gave their homework their best. Then family dinner again a set time so they knew the latest they could start a game that was timed. After dinner some family tv together and off again to game etc. Before school was watching the news and us talking about what was going on in the world in the kitchen whilst we ate breakfast.
I do agree that Fortnite was a particular trigger for bad behaviour. But we talked about it, like they were adults. You tell him what you observe, I can see that Fortnite makes you feel frustrated, what do you think you can do about that? What can I help you with? Let him figure it out.
Also tell him you understand that it is hard to stop the game even more so if it is open ended like Minecraft, there is no end of game. Ask him to come up with a screen time schedule that he thinks is fair and corresponds with his mates playing too. Then look over it, see what he is suggesting. For mine they did chores too, dishwasher in the morning and emptying bins, plus stripping their beds etc. All this behaviour facilitated them choosing what they wanted to do with their free time, which of course is being online.
We had sit down talks at the table for anyone including parents to air their grievances in a positive manner so instead of I hate it when this happens, more I would like it if that happens instead, name the behaviour you want to see. The children felt empowered to ask for table talk and request later bedtimes, or a phone upgrade, whatever. It worked for us.