So, at this point, if you’re not a techy, where can you still publicly post information? TikTok, I think?

TikTok or any such other crap is not publicly.

It takes like, $0 and a cup of coffee at most to start a simple page in neocities for a simple announcement. Heck, in the absolutely simplest cases available you can literally upload your own announcement (a picture, a PDF or smth) to ufile.io and just pass around the link to that.