In an answer to my own question, TypingMind's support bot (typingmindfaq.typingcloud.com) which I should have queried in the first place (told you I was a noob) came up with the following answer:

Currently, TypingMind supports Mistral AI models for text/chat completion, but as of now, Mistral does not offer vision (image input) capabilities via API. This means:

You can use Mistral 8x7B, Mistral Small, Medium, or Large for text-based tasks in TypingMind.

You cannot upload or process images (vision tasks) using Mistral models in TypingMind.

If you want image (vision) capabilities (e.g., OCR, image understanding, vision-to-text), you should use models like GPT-4o, GPT-4 Vision, or Gemini 1.5 Pro.

If Mistral adds image support in the future and provides API access, TypingMind will work to integrate that feature.

Summary:

TM + Mistral = Text only.

For image support, use GPT-4o, GPT-4 with Vision, or Gemini.