IFSIM is one of the friendliest communities of pilots and controllers you will ever meet. I have known them and talked to them on discord for a while now and currently under training to become an ATC controller. The in depth detail of what they do is amazing. From using the official departures and approaches of airports to having dedicated discord voice channels for; clearance delivery, ATIS, Ground, Tower, Departure, Center, Approach, Emergency and even a dedicated training channel for people like me to learn. The Controllers are amazing using official charts and if you get something wrong, they will politely correct you. The CEO Keith is a good guy just to talk to in general organizing of events and just controlling everything.
They hold events on the free flight server regularly for pilots and controllers to hone their skills, using the exact pilots language for a realistic experience that every pilot should enjoy.
I thoroughly recommend IFSIM to any of my friends if you love a realistic infinite flight experience