We officially have zero obligations, but he's making a fuss because I play games on Discord with guys from my sports club, and now he actually wants to dictate my training times. Since when does a situationship have admin rights over my entire life?

In short: If you don't subscribe to the relationship plan, you won't get admin rights over your life. What's happening here is the classic case of cherry-picking: You want the comfortable, non-committal nature of a situational relationship, but you're acting like a jealous control freak in the final stages. Your club, your friends, and your Discord server belong to you—they're not a front yard they can dig up as they please. If someone tries to censor your calendar and contacts without committing themselves, it's not about love, it's about pure possessiveness. Make it crystal clear: "We're not in a committed relationship. My training schedule and who I talk to on Discord are my own decisions—if you can't handle that, we'd better end this immediately." Draw the line firmly now. You're an independent person with your own daily life, not a side project to be managed after work.