It depends on the popularity and security. Do you still think here and reddit is popular? I doubt. Too much ads, scams, nonsense. I don't think new reasonable people will like here.
If you use telegram, you can control the group. You can allow new user to join and kick out annoying person (who just posts ads or nonsense).
Right now, I think telegram is going to become the most popular secured communication tool.
BTW: Here (bitcointalk) is just becoming the announcement place. Not the place for deep discussion.
Sadly, here and Reddit are very popular. A few different forum sites have asked me to move our discussions onto their sites, and part of the problem is keeping everything current. Each new site means that each post that any member of the Foundation does needs to also be copy and pasted onto another site.
On this thread I deliberately didn't take control of the moderation because I didn't want people to think we were censoring them. I almost immediately regretted it and I emailed the mod and asked for control of the thread.
He said that it was too late.
Now I feel good about it once again. We are all on the same playing field.
If you want to lead the charge and run the telegram discussion, I will set up a telegram account and make you a mod. We can use all the help we can get in regards to getting the word out.
As for the slack channel; it currently is only for the TRC Foundation members. A lot of private information has been exchanged on there.