I have worked for companies with thousands of employees, yes. It helps to be right about the cost, security, and usability benefits of using FOSS and be able to stand your ground and argue valid points.
But I do prefer companies with less than 100 people.
I make it very clear at the interview stage that I use Linux. Its never been an issue.
If someone tried to force me to use proprietary software, I’d say no. If they wanted to fire me over that, it would be ridiculous. It’s free and easy to support FOSS. Its costly & difficult to support proprietary software, so its not a hard sell.
I tell customers to use Libre Office. I tell them its free, cross platform, give them a link to download it, and ask if they have any further questions.
If they said IT issues, I’d ask to talk with their IT department. Its not difficult to get IT to install trusted, open-source software.
Lots of justification in this. Just be the change you want to see.
I only work with libre formats at work. If someone wants to collaborate, they can easily install libre office or gimp or freecad or gnu cash or whatever. Most libre software is free and cross-platform.
Its possible with anonymous data. But you do need other user’s data. So it would need to somehow be not just self-hostee but also federated. With lots of dsts from other servers