Would you consider Zoho a "real" competitor?
Would a Nextcloud instance work?
I've checked out Nextcloud a few times, but it really needs a sizeable and trustworthy brand that would host it for you, allow you to point a custom domain at it, and provide zero config email/calendering out of the box.
I'd trust Mozilla.
Amazing that GSuite's only real competitor in 2020 in Office365.