I teach a class in which students write several lab reports in LaTeX, and up until very recently I required students to use Overleaf. This allowed groups of 3-4 to write lab reports in LaTeX with real-time collaboration. It was pretty awesome!
All of a sudden today, people in my class started noticing that the ability to collaborate on a given document with more than 1 other person was now behind a paywall. Since the minimum group size in my class is 3, Overleaf is no longer nearly as useful to us. (While it is possible that my institution will one day provide a site license, that would take ~a year, and I'm ideally looking for solutions that I can implement this week!)
Are there any free alternative online LaTeX editors that allow real-time collaboration, but do not charge for the ability to have multiple collaborators?
(By the way, I am aware of this question, but the question and its answers focus on editors that do not require a sign-in, and not on the ability to collaborate. Requiring a sign-in is not the issue for me.)