Well, I guess Nextcloud has all of these. Not sure if there is something more specifically made for your usecase, where it's still one single application and not three.

I’ve been thinking about some similar use cases recently and came to the conclusion that it’s ultimately about packaging. All the functionalities that are needed are fairly readily available (other replies here have aome good suggestions in Nextcloud and self-hosted Odoo), but the real challenge is to make it easily deployable into and accessible for the community.

My thinking was specifically for the idea of easily connecting and organising building tenants. I want to get to the point where one (or a few) tenants can get together, set up a single boxin a flat in the building, and distribute QR codes to the other tenants that will allow them to access some kind of virtual building community hub. If you’re reliant on a lot of technical know-how to set up or maintain this, that’s going to severely limit its usefulness.

I like the Nextcloud suggestion.

Still if you're open to hosting or can find hosting service, then Odoo Community could work. It's a ERP/CRM suite with several useful modules, including:

• Discuss (Slack-like messaging with file attachments)
• Calendar, To-Do, and Project for task management
• Website & eLearning modules for additional functionality

Its unfortunate that some modules & features are withheld for selling people on Enterprise. Could be soltuion to look into but is proably overkill. Similar to Odoo, ERPNext doesn't do feature lockout but I don't know if they have similar modules or not.

You could certainly massage Grist into something that checks most of those boxes might have to get creative with widget fields to have people mark themselves as active on a given task. But similar to some advanced notion templates databases can back end most anything you can think of!