https://www.mudlet.org/
https://github.com/Mudlet/Mudlet

It's a free and open source client to run MUD games. MUD games are text based, multiplayer. Not all MUD games have open source, but then they are multiplayer games so even if you could host your own server, these games are based around story and not gameplay so multiserver way of playing is less appealing. Besides if people want to play the same story they need the same files. So I'm not sure where these games stand in terms of being free and open source. I hope you can take a look into it. It sounds like a nice platform to play online text based games on Linux.