Not all architectures are supported by llama.cpp . The GGUF format encodes the NN in a standardized way, but then you need code that can use that NN structure.

I understand that llama.cpp could only output text, last time I checked (I do not know how to find a good source for that though).

See https://github.com/ggml-org/llama.cpp/blob/master/src/llama-... , the

  enum llm_arch {

I haven't used llama.cpp for image generation either but I recall an issue about it. Unfortunately I can't pinpoint it now and there is the older closed issue https://github.com/ggml-org/llama.cpp/issues/4408 so unless mtmd supports also multimodal outputs out of the box safe to assume output is still limited to text.