Hello.

I am a long time Ubuntu and Fedora user and this is probably off Topic but we solved similar issues this way.

Once set up correctly we can't go past AWS S3 buckets for storage and access, Cognito for user management and Cloudfront for automatic site rebuild, etc. You describe below pretty much how our system works on AWS. We have no database and no server.

Cloudfront has the advantage that if in the unlikely circumstance, our site is hacked, Cloudfront sees the change and rebuilds to the original page automatically.

We have static web site menu pages built on Ubuntu using HuGo a static web site builder to display documents to relevant users, all we need to do is upload documents to the free S3 buckets of which we have several, some with folders. Our upper level managers have no programing skill can handle highly secure documentation with no understanding or effort.

There is a little more to understand but these serve our purposes very well for a wide range of management,  users and administrators.
AWS Cognito and Cloudfront need some setting up but once done no further Admin is necessary.
Much of our setup is non Public access, being AWS we have no security issues.
The only html/css programing was some alteration to basic HuGo static web site themes.

For members who leave, we simply change their password, when a new member arrives we allocate that password to the new member's email address.

For contributor input generic blog themes work very well.
AWS services cost us a few dollars a month, about 1/4 the price or less of an ISP because there is no server system and infrequent access. We have maybe 50-100 clicks a day at most and the cost for that is .02 to .08 cents per day.

I hope this is of help.
Roger

Asking for a friend. She is on the committee of a small non-profit group with 
ten members. They're looking for a free/low cost solution for storing 
committee correspondence, files, images, etc in one central place.

Currently the individual members share files they own via Google, and upload 
files to their Facebook group, or keep files on their own computers. It's 
messy, 
and they need everything to be in one place with the ability to easily control 
permissions. For eg when a committee member leaves, they want to be able to 
press a button that removes all access for that (former) member but their 
files 
will remain. And they want different levels of access, for e.g. the executive 
can see certain files but not general committee members (for issues where 
privacy is a concern).

They need a structure that is easily managed, such as for eg sections on the 
various committee roles and relevant documentation for that role; a section 
for storing minutes; a section for current works in progress; collaborating on 
documents, etc.