There's a discussion over on Privacy Guides@lemmy.one about using Matrix/Element (an open messaging protocol and leading client) for secure DMs on here, as you can add your Matrix ID to your account here and it becomes a secure messaging link on your profile. If I've done it right, you can see this in my profile as well as various ones in the first link.
However, it strikes me that, as a federated alternative to end-to-end encrypted messaging apps like WhatsApp, because you can start groups (public or private) and share your contact information without having to give out your mobile phone number, it might be useful for a team of moderators to discuss moderating issues on their community. At least until we get proper moderating tools and encrypted messaging here.
Anyway, worth considering as the community expands and we need to draft in more help. It certainly gave me the kick in the pants to register an account there. Even though I did a lot of reading on the subject and installed the app a few months back, I couldn't see the usefulness to myself at that point. However, just having a means to enable secure DMs on here suddenly shifted it up my list of things to do. If it helps with moderating communities on here, then that's gravy.
Alrighty, that's working - I get a choice of apps: Element, SchildiChat and FluffyChat (I did install the first and last when I did my research). It looks like when you decide which app to use once, Matrix then only offers that option but there is a "change" link under the app information.
And that gets you back to giving you the three options.
I've sent you a test message through Element but will check it out through FluffyChat later.