they're requiring phone number validation just after registration or you run the risk that they suddenly lock your account, demanding a phone number for "abuse prevention". depending on ip reputation and possibly other factors it may be impossible to use it in the first place without providing a phone number.

But I have to agree: Eventually, management will start to more aggressively monetize it (i.e., "pull the rug from under their free users").

Truly free (e.g., IRC) alternatives seem like the only long-term solution, otherwise people will keep stumbling from one commercial platform to another, because they never last.