OpenCode has “providers” for many (many!) other services, but these are almost all unofficial and against ToS (Anthropic being famous for ban-hammering people).
Or choose Oh My PI [2] for batteries included
[1] https://github.com/earendil-works/pi [2] https://github.com/can1357/oh-my-pi
To preempt certain replies, yes, I know you can pay API prices and use whatever harness you want.