Agreement:
* Fine with
* Happy with
* Content with
* Agreeing to
* Agrees to
* Doesn't mind
* Comfortable with
* On board with
* In agreement with
Acceptance:
* Tolerates
* Accepts
* Doesn't object to
* Has no issue with
Neutral:
* Doesn't matter to
* Doesn't mind
* Doesn't have a problem with
Informal:
* Cool with
* Down with
* All good with
More formal:
* Approves of
* Sanctions
* Concurs with
The best synonym will depend on the specific situation and the desired level of formality.