I just fixed a mountain of issues around Gemini (including fixing streaming) and added Gemini 1.5 Flash support as well.
My strong recommendation would be to keep to the 1.5 models, flash is great, it is fast and cheap and does a pretty good job at summarizing.
https://github.com/discourse/discourse-ai/commit/d5c23f01ff69cd6641160ba14030c2c31e092fd5