It has been tried over the years. The question really is how much the employees understand and care about digital sovereignty. If they keep complaining because they have to learn new tools, they will eventually go back to Microsoft...
There are a lot of tech people who appreciate open source software and understand the benefits of digital sovereignty but its rare for them to have the final say in most orgs.
Just about every org in my country uses Microsoft's email including universities, government, schools, businesses. I am sure it has some features that make it a good choice but its is unusual for any product to have practically 100% market share and no competition regardless of technical or usability advantages. Microsoft has huge resources and knows how to win customers.
Arch users are the vegans of the Linux world.
I use Arch, btw
Why would Arch be in that position?