I didn't realize that langchainrb had included ollama. That's really cool.
Personally, I prefer to wrap my own classes around something like ollama since it does provide an API. And a lot of knowledge from those kinds of gems could be taken. I am planning an episode of vector searching with meilisearch, but am waiting for it to be released/stable so that could take a bit.
My main thing against something like langchainrb is if it is going to be a core part of my application. If it is, then I probably wouldn't want to rely on a gem to provide core functionality. If it is a nice-to-have feature, then I would add it to my list of considerations when making feature.