Most (probably all) open model providers implement OpenAI-style API. If your app's already using OpenAI models, it's as simple as swapping the endpoint and the key to switch to these models.

Open models have a lot of providers. You can even just use OpenRouter if you want.

In theory Cerebras have a developer subscription model you can use, but they seem to have stopped new signups. So per sibling, OpenRouter and per-call pricing is the answer for now.