I think it really helps to open with "I have a speech disability". Maybe even "I have a speech disability, so if it's hard to understand me sometimes, it's not because I'm nervous. I'm actually very excited about this opportunity"! Don't say the word stutter, because fluent people often associate that word with a very mild "everyone does it sometimes!" type of disfluency. Disclosing you have a disability will make it a lot more likely that the interviewer 1. is more lenient with grading communication because they know it's not your fault 2. may actually increase your chances because the interviewer may feel bad or have DEI incentives that make it less likely to reject you