On: Twitter starts to require login to view tweets

[fsiefken]

gemini https://gemini.circumlunar.space/

fediverse: mastodon, pleroma, pixelfed

indieweb: https://indieweb.org/

twtxt: https://indieweb.org/twtxt

scuttlebutt https://scuttlebutt.nz/

hypercore https://hypercore-protocol.org/ (see iris.to for an implementation)

https://quitsocialmedia.club/solutions

[kmstout → fsiefken]

Also, hit up a bulletin board or two: https://www.ipingthereforeiam.com/bbs/?step=name&all=0

[richardfey → fsiefken]

On the IM side there's also https://delta.chat/en/

[p4bl0 → fsiefken]

I would add RetroShare to the list.