For LLMs, the closest thing that comes to mind is KoboldAI[1]. The community isn't as big as Stable Diffusion's, but the Discord server is pretty active. I'm an active member of the community who likes to inform others on it (you can see my previous Hacker News comment was about the same thing, haha).

Like Stable Diffusion, it's a web UI (vaguely reminiscent of NovelAI's) that uses a backend (in this case, Huggingface Transformers). You can use different model architectures, as early as GPT-2 to the newer ones like BigScience's BLOOM, Meta's OPT, and EleutherAI's GPT-Neo and Pythia models, just as long as it was implemented in Huggingface.

They have official support for Google Colab[2][3]; most of the models shown are finetunes on novels (Janeway), choose-your-own-adventures (Nerys / Skein / Adventure), or erotic literature (Erebus / Shinen). You can use the models listed or provide a Huggingface URL.

[1] - https://github.com/koboldai/koboldai-client (source code)

[2] - https://colab.research.google.com/github/koboldai/KoboldAI-C... (TPU colab; 13B and 20B models)

[3] - https://colab.research.google.com/github/koboldai/KoboldAI-C... (GPU colab; 6B models and lower)