If you were using Signal just for SMS, none of your messages were secure anyway since the SMS protocol itself is not–defeating the purpose of signal. And if you had already convinced people to install Signal by using SMS as a caveat, you can just continue contacting them through the app.
I was able to convince pretty much everyone who matter in my life to install Signal and they all love it because WhatsApp has become too cluttered and spammy.
Postimages already has official plugins for several forum softwares. I am sure one of them could be tweaked for use in Kbin and Lemmy instances. And postimages themselves might help in this, if contacted.
I have for long used postimages.org whenever I needed one. But imgbb.com is also an equally good option.
There are a lot of good suggestions here. Just to add on to it, I have been using Skiff Pages as an alternative fog Google Docs for a while now, and I have been happy with it. They have a better UI and feels less clunkier than CryptPad. They also offer couple of other services such as Drive and email, which you can check out as well.
Many people forgot, many others now think that he is the villain of the story just because he did what he had to do to save his life, a whole lot don’t care because ‘they have nothing to hide’. For what it’s worth, people who actually care about their privacy is a very small minority in pretty much all countries.