A free client-server product for collaborating on a business plan?

Question

CMS

Given:
There are about 5-7 organizations that prepare reports in Excel.
Report files up to 200 MB.
Excel is used as a multi-page calculator, the output of the entire work is an A4 sheet with final results.
Purpose: To facilitate the work with reports on low-powered computers.
Remedy: Lightweight SED, essentially Excel functions.
Examples: Google Sheets is a great solution, but it all comes down to a condition.
Condition: It is possible to deploy EDMS only within the "framework" of the enterprise. There is power for this.
Do without increasing the power of computers.

Answer 1

Look at onlyoffice.org

Answer 2

Why not talk to Google?
In any case, something sensible and free is now hard to find.
As an option - LibreOffice Base (free) + Terminal access (unload weak computers), but to write a project in Base you need smart specialists.