This is where this kind of companies come into play : https://indie.host https://indie.host [french link] You have one person to talk to, they manage RocketCha

This is where this kind of companies come into play : https://indie.host https://indie.host [french link] You have one person to talk to, they manage RocketChat, NextCloud (with an office suite, agenda, files), Jitsi, Discourse, CodiMD, all of this with a single sign on for your coworkers. All for 10€/month/user. It's not as integrated as say a full microsoft suite, but probably one order cheaper.