So this is the same Slack that wrote a love letter [0] to Microsoft about competing with them and now they are crying to the EU to investigate them over Teams because they failed. Sounds like a chicken blaming the wolf for eating them after inviting it to a dinner party. After all, they asked for it. [0] https://slack.com/intl/en-gb/blog/news/dear-microsoft
If you're going to claim that Microsoft including Teams in Windows is "competing" then Slack is simply "competing" by utilising the EU.