I set up open tools for working together: Nextcloud for files, shared documents and calendars, Matrix for encrypted team communication. Both run on your own infrastructure.
What I take on
The consulting beforehand: which system fits the way you work, what it presupposes, and what the change means for the people who are meant to use it every day.
Then the installation and the adaptation to your organisation. Nextcloud and Matrix bring a great many settings with them, and the defaults rarely fit straight away.
Why on your own infrastructure
Because the data then stays where it belongs. Whoever puts their files and conversations on someone else’s service gives up control over them, and does not get it back when that provider changes its terms.
There is a price: a self-hosted system needs someone to look after it. If you cannot provide that, you are better off with a hosted offer, and I will say so.
What comes afterwards
Running the system, maintaining it and introducing your people are part of it if you want them to be: consulting, prototype, delivery and upkeep come from one hand, here as with any other development. Which of it you take on yourself is your decision.