At our startup, we rely on nextcloud (self hosted on a root server from a German hosting provider) + libre office for all of the more „mundane“ parts of our business. To be fair though, we’re in a very niche market (offshore wind) running at a very different speed compared to your regular startup. It’s been a conscious choice to run everything on foss and self host as much as we can. Big plus for nextcloud: the sync client works reliably even on intermittent and extremely slow connections (offshore). The overhead of maintaining nextcloud ourselves is manageable (yet another docker container) and it’s been astonishingly reliable ever since we got started. For us, maintaining control over data is paramount, so it matters greatly to us. If one day the overhead should become too much, I’d probably move our nextcloud over to a nextcloud provider.