Incorrect. Nextcloud integrates everything in a much tighter package than Office365, which I cannot stand. Office peaked with Office 2k. This online/cloud stuff is just effing awful.
My business resells Microsoft Office 365 products (yeah, I know, but there are no FOSS systems with comparable feature sets for businesses...)
One problem we ran into a lot was that if a customer already had Office 365 through GoDaddy, we would have to basically delete their whole organization and manually import all users, emails, and settings from the GoDaddy managed O365 to ours. The reason for this is that when a company buys MS O365 products through them, GoDaddy sets it up as a Federated domain. This means that GoDaddy and GoDaddy alone gets to manage the MS O365 tenet, you cannot transfer it out, and if you cancel service with GoDaddy, they delete your account and all your data.
Then I found this guide: https://tminus365.com/defederating-godaddy-365/
I just used it to successfully de-federate my first GoDaddy account, retaining all my customer's emails, files, and Active Directory (ahem, Entra ID) information.
Screw you, GoDaddy!
Discussion
Nextcloud is great for file sharing but it doesn't have the email features of hosted exchange.
OK. I suppose that is a limitation, if you rely on email to run your business these days... Ugh...
Basically all small businesses still rely on email. Hell, some still use fax machines...
Please don't talk to me about fax machines... Ugh.
I hate email.
Nostr has had a real damping effect on my tolerance for bad systems...
For my business we run Libre Office, Mailcow, FreePBX, and a self hosted Wordpress site for visibility. And I spend too much time keeping it all running. They want turn-key solutions with very little maintenance. And they don't mind giving money to an evil empire like Microsoft every month. I do at least try to inform them of the benefits of running FOSS software, but very few want to make the switch.
I use Mailcow for email internally but I wouldn't resell it to customers because of all the integration features of O365